Curcumin inhibits lipoxygenase by binding to its central cavity : theoretical and X-ray evidence

INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE 6: 521-526, 2000
Curcumin inhibits lipoxygenase by binding to its central
cavity: theoretical and X-ray evidence.
EWA SKRZYPCZAK-JANKUN1,2, N. PATRICK McCABE2,3, STEVEN H. SELMAN2-4 and
JERZY JANKUN2-4
1Instrumentation Center, College of Arts and Sciences, The University of Toledo, Toledo, Ohio 43606; 2Urology
Research Center, Departments of 3Urology, 4Physiology & Molecular Medicine, Medical College of Ohio, Toledo,
Ohio 43614-2589
Abstract. Many lipoxygenase inhibitors including
lipoxygenase 1 (L1), which was also the first
curcumin are currently being studied for their anti-
lipoxygenase isozyme to have its three dimensional
carcinogenic properties. Curcumin is a naturally
X-ray crystal structure solved [1, 2]. Nomenclature
occurring polyphenolic phytochemical isolated from
for the lipoxygenases found in mammals arises from
the powdered rhizome of the plant Curcuma longa
the positional oxygenation along the carbon chain of
that possesses anti-inflammatory properties and
arachidonic acid (AA). Mammalian lipoxygenases
inhibits cancer formation in mice. Recently it was
(LOXs) characterized thus far include 5-, 8-, 12-, and
shown that the soybean lipoxygenase L1 catalyzed
15- type LOXs. Modeling of human lipoxygenases
the oxygenation of curcumin and that curcumin can
using pair-wise sequence identity has been performed
act as a lipoxygenase substrate. In the current study,
previously [3] and several theoretical models of
we investigate the fate of curcumin when used as a
substrate mechanisms of action were discussed. To
soybean lipoxygenase L3 substrate. By use of X-ray
date, rabbit reticulocyte 15-LOX is the only
diffraction and mass spectrometry, we have found an
mammalian LOX for which the three-dimensional X-
unoccupied electron mass that appears to be a
ray structure has been obtained [4].
unusual degradation product of curcumin (4-
The amino acid sequences between plant
hydroxyperoxy-2-metoxyphenol) located near the
and mammalian LOX enzymes show considerable
soybean L3 catalytic site. Understanding how
homology. The soybean lipoxygenases, L1 [1] and
curcumin inhibits lipoxygenase may help in the
L3 [5], are 72% identical in their amino acid
development of novel anti-cancer drugs used for
sequences, but share only 25% sequence homology to
treatment where lipoxygenases are involved.
any mammalian 15-LOX. Overall, sequence identity
between plant and mammalian pairs of lipoxygenase
Introduction
isozymes is 21-27%, while plant pair sequence
identity ranges from 43-86%, with mammalian pair
sequences at 39-93% identity [3]. The highest level
Lipoxygenase enzymes can be found in a wide
of sequence identity between lipoxygenases from
variety of plant and animal tissues. Lipoxygenases
plants and mammals lies in the area of the catalytic
are enzymes that possess a non-heme iron serving as
domain containing the non-heme iron atom.
a catalytic center for the stereo- and regio-specific
Mammalian lipoxygenases are 165-261 residues
dioxygenation of select carbon atoms in
shorter than the plant lipoxygenases and were
polyunsaturated fatty acids containing a 1,4-
pentadiene motif. Eighteen carbon chain fatty acids
believed to lack a N-terminal ? barrel due to the fact
(eg. linoleate) are the primary substrates of the plant
that similarities in the sequence identity of the first
lipoxygenases while the mammalian isozymes mainly
200 residues between pairs of plants and animals
catalyze the metabolism of fatty acids of carbon
never exceeds 15%. Comparisons between various
length 20 (eg. arachidonate). The soybean
mammalian lipoxygenase cDNAs have recently been
lipoxygenases were the first to be characterized and
reviewed [6]. The similarities in sequence data across
are named sequentially beginning with soybean
species lead to the assumption of similar 3
___________________________________________
dimensional structures and the comparison of
Correspondence to: Dr. Jerzy Jankun, Urology Research Center,
soybean L3 with rabbit 15-LOX confirms that plant
Department of Urology, Medical College of Ohio, 3000 Arlington
and mammalian enzymes share the same topology
Avenue, Toledo, OH 43699-0008, U.S.A.; or Dr. Ewa Skrzypczak-
and overall architecture despite differences in size
Jankun, Instrumentation Center, College of Art and Sciences, The
(Fig. 1).
University of Toledo, Toledo, OH 43606.
Email: jerzy@golemxiv.dh.mco.edu
Soybean lipoxygenases play physiological
Ejankun@protein.chem.utoledo.edu
roles in processes such as growth, development,
wound healing and senescence. As the main
substrate for soybean lipoxygenases, linoleic acid is

---

INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE 6: 521-526, 2000
Fig. 2. Curcumin shown in the central cavity of soybean L3. Iron
Fig 1. A Comparison of soybean L3 (blue) and rabbit 15-LOX
is shown in brown color, carbon in green, oxygen in red, hydrogen
(yellow) 3 dimensional structures. Iron is shown as a brown
in white. L3 is shown as a ribbon model with the front part
sphere. Please note the close similarities in topology despite the
removed from the figure for clarity (theoretical predictions based
differences in size (L3: 857 residues; rabbit 15-LOX: 663
on force field calculations).
residues).
metabolized into one of various
aspects of atherosclerosis [22, 23]. As a whole,
hydroperoxyoctadecadienoic acids (HPODEs). The
mammalian LOXs and products produced by
biological significance of the HPODEs has yet to be
substrate metabolism play significant roles in cancer
fully characterized. Mammalian LOXs use
cell growth, metastasis, invasiveness, and cell
arachidonic acid as the primary substrate which, once
survival.
released from the mammalian membrane through the
Many lipoxygenase inhibitors are currently
action of PLA
being studied for their anti-carcinogenic properties.
2 or a combination of other
phospholipases [7], can be metabolized into
Curcumin is a naturally occurring polyphenolic
leukotrienes (LT), lipoxins, or into eicosanoids.
phytochemical isolated from the powdered rhizome
Leukotrienes and 5-HETE (hydroxyeicosatetraenoic
of the plant Curcuma longa. Curcumin has long been
acid) produced via the 5-LOX pathway have been
known to possess anti-inflammatory properties and is
shown to be active in promoting asthma and allergic
a commonly used spice in Asia. It has more recently
airway inflammation [8]. Inhibitors of the 5-LOX
been reported to inhibit tumorigenesis in mice [24].
pathway have chemopreventive abilities in animal
Further, curcumin has the ability to decrease the
lung carcinogenisis [9, 10] and block the oxidation of
formation of 5(S)-, 8(S)-, 12(S)-, and 15(S)-HETE in
several potent carcinogens [11]. 5-HETE has the
mouse epidermis [25].
ability to stimulate growth of lung cancer cells [12],
Here we investigate the fate of curcumin
prostate cancer cells [13], and 5-LOX inhibitors have
with soybean lipoxygenase L3. Another group has
the ability to decrease cell proliferation and trigger
studied the soybean L1 catalyzed oxygenation of
apoptosis [14]. 12(S)-HETE, the major metabolite of
curcumin [26] and shown that curcumin can act as a
the 12-LOX pathway, has been shown to correlate
lipoxygenase substrate. Their data and the data
with metastatic potential [15] and stimulate the
presented herein, using soybean L3, lead to the
expression of integrin receptors leading to increased
assumption that curcumin can inhibit lipoxygenase
tumor cell adhesion [16]. Also, 12(S)-HETE can
activity by blocking the active site. By use of X-ray
activate PKC, which mediates the secretion of
diffraction and mass spectrometry, we have found an
cathepsin B, a cysteine protease that has been shown
electron mass located near the soybean L3 catalytic
to be involved in tumor metastasis and invasion of
site. This mass appears to be an unusual degradation
colon cancer cells [17]. In prostate cancer patients,
product of curcumin. Understanding how curcumin
elevated 12-LOX mRNA levels were shown to
interacts with soybean L3 may explain how curcumin
correlate with poor differentiation and cancer cell
inhibits lipoxygenases and HETE formation. Due to
invasiveness [18]. Additionally, 12-LOX in human
the lack of structural data for human LOXs,
prostate carcinoma stimulates angiogenesis and
researchers are still modeling human LOXs using
tumor growth [19]. Recently it was shown that 5-
soybean enzymes because of their availability and
HETE and 12(S)-HETE directly stimulate pancreatic
highly characterized structures. Use of plant
cell proliferation and that LOX inhibitors can induce
lipoxygenases to model mammalian LOXs will prove
apoptosis and cell differention [20]. 15-LOX and its
highly beneficial and aid in structural
products have been linked to cell maturation and
characterization, mechanism elucidation, and
differentiation [21] as well as implicated in several
possibly the discovery of novel inhibitors of LOXs.

---

INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE 6: 521-526, 2000
Materials and Methods
fragment), ?Ghb and ?Gion represent the contribution
from an ideal hydrogen bond and unperturbed ionic
Obtaining the Starting Structure. All molecular
interactions respectively, ?Glipo represents the
modeling and structure visualizations were done on a
contribution from lipophilic interactions which is
SGI workstation using the InsightII program package
proportional to the lipophilic surface Alipo , ?Grot
from MSI [27]. Atomic coordinates of soybean L3
represents the contribution due to freezing of internal
were as deposited in the Protein Data Bank (PDB
degrees of freedom in the fragment, NR is the
entry lLNH). Hydrogen atoms were added with
number of acylic bonds, ?R is the deviation of the
appropriate charges assigned throughout the molecule
hydrogen bond length from the ideal value of 1.9 Å,
of lipoxygenase assuming physiological pH 7.4.
?? is the deviation of the hydrogen bond angle from
Partial and formal charges were assigned accordingly
the ideal value of 180o. In general, a higher Ludi
to the extensible systemic force field (esff).
score (0-1100 in range) represents higher affinity and
stronger binding of a ligand to the receptor
Docking. The docking module enables the calculation
In addition, the Ludi score can be related to
of non-bonded energy between molecules assuming
the dissociation constant Ki. Ludi Score = -100 log
that fragments of the molecules are flexible. This
Ki.
program uses a score (Ludi) to quantify ligand-
receptor binding for a fully energy minimized
Isolation of soybean lipoxygenase (cutlivare Beeson
structure. The following parameters were used:
80) was done as previously described [5]. Fractions
radius of subset from Fe atom = 12 Å, maximum R
from a chromatofocusing column were collected
change = 6 Å, maximum number of structures
using a Gradi-Frac machine (Pharmacia Biotech;
minimized = 7 (this number was usually higher since
Piscataway, NJ) and the appropriate peek was
many different initial structures produced the same
concentrated using Centricon concentrators
minimized structure), minimum steps = 100 or less if
(Millipore; Bedford, MA). The concentrated protein
the maximum derivative was smaller than 0.01
solution was dialyzed against Tris buffer (pH 7.0) to
kcal/mol/Å, MC temperature = 20, energy tolerance =
remove the histidine buffer and was purified to a
5000. Following this step, all structures were subject
single band by SDS-PAGE.
to simulated annealing where the temperature was
raised to 500K then gradually reduced to 300K, after
Crystallization and data collection. Protein crystals
which 5 structures with a minimum potential energy
were grown using the “sitting drop” method as
were subjected to molecular dynamics for 1000
described before [5]. Curcumin was dissolved in
picoseconds. The structure with the minimum
ethanol and added to the crystallization dishes so the
potential energy was accepted as the most probable
final concentration of protein to curcumin was
one.
approximately1:1 with ethanol <2%(v/v). The
The Ludi scoring method of interactions
crystals became pale yellow and data was collected at
between a protein and its ligand was used to quantify
room temperature using a RAXIS IV imaging plate
the binding characteristics of curcumin to
detector with a Cu rotating anode and focusing
lipoxygenase. The Ludi method for de novo design
mirrors. Crystal-to-detector distance was set at 140
of ligands for proteins (i. e. enzyme inhibitors) is a
mm with an exposure time of 12 minutes per frame
method for screening a large number of compounds
and 2° oscillation. To avoid as much bias as
by analyzing the geometrical fit of given chemicals in
possible, crystals of approximately the same size
the designated protein binding site. Other
(~0.5mm) and shape were used to test varying
determinants of good binding are also calculated and
soaking times and total exposure. After 45-90min
include hydrogen bond formation, lipophilic
(depending on crystal size), the crystal exposed to X-
interactions, ionic interactions, and acylic
rays had changed to a purple color. This change of
interactions. However, Ludi can also score protein
color was especially easy to notice on crystals bigger
ligand interactions by statistically evaluating the fit of
than the diameter of the collimator (0.5mm), where
all potential ligands determined by the Docking
only the portion of the crystal irradiated by the X-ray
module. Ludi Score = -73.33 mol/kcal ?G, where:
beam turned purple with the rest of the crystal
?G = ?Go + ?Ghbf(?R)f(??) + ?Gionf(?R)f(??) +
remaining yellow. This phenomenon was not
?GlipoAlipo + ?GrotNR ?G; ?Go represents the
observed in the curcumin solution when exposed to
contribution to the binding energy that does not
X-ray or in the crystal (no curcumin) when exposed
directly depend on any specific interactions with the
to ambient light. The crystal soaked in curcumin
receptor (i. e. the contribution to binding energy due
remained purple for several hours following X-ray
to loss of transitional and rotational entropy of the
exposure and was still a light pink 24 hours

---

INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE 6: 521-526, 2000
following. The reflections corresponding to the
soybean L3 peak were collected and purified (Fig 3)
“purple” phase were processed and integrated using
as described in Materials and Methods.
Denzo and Scalepack [28] resulting in three data sets
corresponding to 15, 48, and 70 hours of soaking
Crystallography of the lipoxygenase-curcumin
time with not more than 6 hours of total X-ray
complex. A change of color of lipoxygenase
exposure per crystal. The data extended to a 2.1–2.2
solutions has been previously observed and described
Å resolution with 92-95% completeness and 6-8% of
[33]. It has been observed in lipoxygenase crystals in
Rmerge per set.
the presence of peroxides, such as 13-hydroperoxy-
9,11-octadecadienoic acid (13HPOD) and cumene
Mass spectroscopy. L3 crystals soaked with curcumin
hydroperoxide [34]. The same phenomenon was
not exposed to X-ray and crystals after exposure to
noticed (i.e. the color change to blue/purple) with the
X-ray were dissolved in deionized water and
iron complex [Fe(bppa)(t-BuCOO)]2+ when its t-
analyzed by mass spectrometry at the Protein
butyl carboxylic acid ligand is substituted with t-
Structure Facility, University of Michigan, Ann
butyl- or cumene hydroperoxide [35]. This color
Arbor, Michigan. Electrospray Ionization (ESI) mass
change is associated with the formation of an
spectroscopy was done using the VG Fisons
unstable complex, wherein the peroxy ligand is
"Platform" single quadrupole mass spectrometer (m/z
bound to the iron atom. Our experiments provide
limit 0-3,000). Samples were introduced into the
evidence that such complexes can exist longer, from
mass spectrometer as H2O solutions by flow injection
several hours to a few days, when “trapped” in a
at 5 microliters/min. Samples were examined in
crystal. In the case of the curcumin-L3 complex, the
positive ion mode to look for protonated ions in the
change of color was not observed in the crystals not
0-3000m/z region, which was later electronically
illuminated by X-rays. This leads to the assumption
refined to give an expanded region of 0-500m/z. It is
that a photodynamic reaction is necessary for the
important to emphasize that in some cases molecules
change of color to occur. It is known; however, that
carry positive charges even without obvious
curcumin can be photobleached, especially by shorter
chargeable sites, possibly because the charging can
wavelengths of the light [36, 37]. The radical change
be affected by gas phase proton affinities [29-32].
in the crystals color, from yellow to purple, occurs
only under X-ray illumination in both ambient light
Results and Discussion
and in the dark. This leaves no doubt about the
photodynamic characteristics of the observed
Molecular simulations. The size of the soybean L3
phenomenon. Also, since the reaction takes place in
molecule exceeds the dimensions of the program for
the crystal, it is obvious that the curcumin molecule
molecular simulations; therefore, the protein was
would have to be near the iron atom and in such an
restricted to radius of 20 Å around the proteins non-
orientation that allows binding between the iron and
heme iron. This volume contains several channels
the created peroxide.
enabling movement of the curcumin into the central
The crystal unit cell was isomorphous
cavity. Our calculations show that curcumin can bind
monoclinic C2, (a=112.8, b=137.3, c=61.9Å,
to lipoxygenase in the central cavity close to the iron
?=95.5o) with that of the wild enzyme (a=112.8,
(Fig 2). The calculated affinity of curcumin for L3
b=137.4, c=61.9Å, ?=95.6o). The structure of this
reaches the high value of 1.06 x 10-10M. This finding
complex was solved by molecular replacement using
supports the hypothesis that the anticancer activity of
native L3 as the starting model (PDB entry lLNH
curcumin could be linked to lipoxygenase inhibition.
with subtracted H2O molecules). The electron
Dietary curcumin consumption levels can be high
density maps (resolution 8-2.2Å, 36325 reflections,
with no known toxic effects, but due to low water
R=24% with only protein atoms included) clearly
solubility only a fraction can enter the circulation.
show an unoccupied electron density near the iron
The high affinity of curcumin for L3, as calculated in
atom. This mass is much too large to be a solvent
the Ludi module, indicates that it possible to inhibit
molecule but smaller than curcumin. The shape and
lipoxygenase with a low concentration of curcumin.
location of the mass do not agree with the forcefield
To verify our theoretical findings we used X-ray
calculated position of curcumin that underwent
crystallographic analyses.
photodegradation during exposure to X-rays (Fig 4).
The shape and volume of the unoccupied electron
Soybean lipoxygenase purification. Soybeans can be
density in the immediate vicinity of the iron suggests
purchased in large quantities, thus providing a steady
the presence of a peroxide (Fig.5, molecule a). Our
supply of protein and easily reproducible crystals for
map does not show any evidence of the
X-ray analysis. Two fractions from the top of the
“prostaglandin-like” molecule (Fig. 5, molecule f)

---

INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE 6: 521-526, 2000
which was found as a product of curcumin oxidation
be identified as potential products of the
catalyzed by soybean L1 [26].
photodegradation of curcumin and are presented in
Fig 5. The strongest candidate is compound 5a, a
Mass spectroscopy. As expected, the mass
peroxide that, while unstable in complex with L3, can
spectrogram revealed numerous peaks that can be
easily convert to compound 5b. Signals of 140 and
attributed to chemicals present in the media used in
157 present on the mass spectrogram strongly support
the crystallization of L3. However, at least four
this assumption. If curcumin were oxygenated
fragments with masses of 140, 157, 176, and 198
leading to the “prostaglandin-like” product (Fig. 5,
appeared on the spectrum from X-ray irradiated
molecule f), it would be present in both spectra, due
crystals but are absent on the spectrogram obtained
to the fact that the experiment was conducted in the
by crystals not exposed to X-rays. These peaks could
presence of oxygen and not in anaerobic conditions.
Lack of any outstanding peak in this region (~400)
indicates that either L3 does not react as L1 or, more
likely, that such a molecule cannot be formed under
the current experimental conditions without
supplemental oxygen. The identity of all other
compounds (Fig. 5, molecules c, d, and e) cannot be
determined with absolute certainty and are outside
scope of this paper.
Fig. 3. The absorbance of different fractions during the
purification of soybean L3. Only fractions indicated by squares on
the graph were used for crystallization. The insert to the left of the
peek is PAGE of this fraction, purified to >95%.
Fig. 5. Possible products of curcumin photodegradation (a-e) and a
suggested product of curcumin oxidation catalyzed by soybean L1
(f).
The structural details of the complex
Fig. 4. L3 molecule with the observed unoccupied electron density
between the photoproduct of curcumin degradation
(mesh) near the iron atom and a curcumin molecule (bold) in the
and L3 will be published upon completion of the
position predicted by the force field calculations. The size, volume
and position of the unoccupied (F
crystallographic refinement. Several conclusions;
o-Fc) difference map indicates the
presence of the photodegradation product of curcumin
however, are quite clear and can be included herein:
corresponding to molecule ‘a’ in Fig.5.
(1) curcumin can penetrate L3 and bind in the central

---

INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE 6: 521-526, 2000
cavity near the iron atom, (2) force field calculations
and for the color change characteristic of the complex
predict a very low dissociation constant of 10-10 M
to occur.
suggesting an very high affinity of curcumin as a
We hope that these observations may prove
lipoxygenase ligand making it a good candidate for
beneficial in the treatment and/or prevention of
an agonist/antagonist in drug design, (3) curcumin
ailments where lipoxygenases are involved.
does not undergo L3 catalyzed oxidation and the
complex is stabile under normal conditions; although,
Acknowledgments
(4) X-ray irradiation elicits a photodynamic reaction
This paper was supported in part by grants
leading to the degradation of curcumin and the
from American Diagnostica, Inc., Greenwich, CT and
formation of a metastabile complex consisting of L3
the OBR Research Challenge Grant.
and a peroxy photoproduct, and (5) a certain period
of time is necessary for the photodynamic reaction to
produce enough peroxide molecules to react with L3
Fig 6. Mass spectra of soybean L3 crystals soaked with curcumin,
not illuminated (N) and illuminated (X) by X-rays during data
collection (expanded region from 100-500m/z).

---

References
19.
Nie, D., G.G. Hillman, T. Geddes, et al., Platelet-type
12-lipoxygenase in a human prostate carcinoma
stimulates angiogenesis and tumor growth. Cancer
1.
Boyington, J.C., B.J. Gaffney, and L.M. Amzel,
Research, 1998. 58(18): p. 4047-51.
Structure of soybean lipoxygenase-I. Biochemical
20.
Ding, X.Z., P. Iversen, M.W. Cluck, et al.,
Society Transactions, 1993. 21(Pt 3)(3): p. 744-8.
Lipoxygenase inhibitors abolish proliferation of human
2.
Minor, W., J. Steczko, B. Stec, et al., Crystal structure
pancreatic cancer cells. Biochemical & Biophysical
of soybean lipoxygenase L-1 at 1.4 A resolution.
Research Communications, 1999. 261(1): p. 218-23.
Biochemistry, 1996. 35(33): p. 10687-701.
21.
van Leyen, K., R.M. Duvoisin, H. Engelhardt, et al., A
3.
Prigge, S.T., J.C. Boyington, B.J. Gaffney, et al.,
function for lipoxygenase in programmed organelle
Structure conservation in lipoxygenases: structural
degradation. Nature, 1998. 395(6700): p. 392-5.
analysis of soybean lipoxygenase-1 and modeling of
22.
Yla-Herttuala, S., M.E. Rosenfeld, S. Parthasarathy, et
human lipoxygenases. Proteins, 1996. 24(3): p. 275-91.
al., Colocalization of 15-lipoxygenase mRNA and
4.
Gillmor, S.A., A. Villasenor, R. Fletterick, et al., The
protein with epitopes of oxidized low density
structure of mammalian 15-lipoxygenase reveals
lipoprotein in macrophage-rich areas of atherosclerotic
similarity to the lipases and the determinants of
lesions. Proceedings of the National Academy of
substrate specificity [published erratum appears in Nat
Sciences of the United States of America, 1990. 87(18):
Struct Biol 1998 Mar;5(3):242]. Nature Structural
p. 6959-63.
Biology, 1997. 4(12): p. 1003-9.
23.
Kuhn, H. and L. Chan, The role of 15-lipoxygenase in
5.
Skrzypczak-Jankun, E., L.M. Amzel, B.A. Kroa, et al.,
atherogenesis: pro- and antiatherogenic actions.
Structure of soybean lipoxygenase L3 and a
Current Opinion in Lipidology, 1997. 8(2): p. 111-7.
comparison with its L1 isoenzyme. Proteins, 1997.
24.
Huang, M.T., H.L. Newmark, and K. Frenkel,
29(1): p. 15-31.
Inhibitory effects of curcumin on tumorigenesis in mice.
6.
Kuhn, H. and B.J. Thiele, The diversity of the
Journal of Cellular Biochemistry - Supplement, 1997.
lipoxygenase family. Many sequence data but little
27: p. 26-34.
information on biological significance. FEBS Letters,
25.
Huang, M.T., T. Lysz, T. Ferraro, et al., Inhibitory
1999. 449(1): p. 7-11.
effects of curcumin on in vitro lipoxygenase and
7.
Needleman, P., J. Turk, B.A. Jakschik, et al.,
cyclooxygenase activities in mouse epidermis. Cancer
Arachidonic acid metabolism. Annual Review of
Research, 1991. 51(3): p. 813-9.
Biochemistry, 1986. 55: p. 69-102.
26.
Schneider, C., A. Amberg, J. Feurle, et al., 2-[(4"-
8.
Irvin, C.G., Y.P. Tu, J.R. Sheller, et al., 5-Lipoxygenase
Hydroxy-3'-methoxy)-phenol]-4-(4"-hydroxy-3"-
products are necessary for ovalbumin-induced airway
methoxyphenyl)-8-hydroxy-6-oxo-3-oxabicyclo[3.3.0]-
responsiveness in mice. American Journal of
7-octene: Unusual Product of the Soybean
Physiology, 1997. 272(6 Pt 1): p. L1053-8.
Lipoxygenase-catalyzed oxygenation of curcumin.
9.
Moody, T.W., J. Leyton, A. Martinez, et al.,
Journal of Molecular Catalysis B: Enzymatic, 1998. 4:
Lipoxygenase inhibitors prevent lung carcinogenesis
p. 219-227.
and inhibit non-small cell lung cancer growth.
27.
InsightII, ver. 95.0/3.0.0 User's guide. 1995, San
Experimental Lung Research, 1998. 24(4): p. 617-28.
Diego, CA, USA: Molecular Simulations, Inc.
10.
Rioux, N. and A. Castonguay, Inhibitors of
28.
Otwinowski, Z. and W. Minor, Methods of
lipoxygenase: a new class of cancer chemopreventive
Enzymology, 1997(276): p. 307-326.
agents. Carcinogenesis, 1998. 19(8): p. 1393-400.
29.
Whitehouse, C.M., R.N. Dreyer, M. Yamashita, et al.,
11.
Kulkarni, A.P., Y. Cai, and I.S. Richards, Rat
Electrospray interface for liquid chromatographs and
pulmonary lipoxygenase: dioxygenase activity and role
mass spectrometers. Analytical Chemistry, 1985. 57(3):
in xenobiotic metabolism. International Journal of
p. 675-9.
Biochemistry, 1992. 24(2): p. 255-61.
30.
Covey, T.R., R.F. Bonner, B.I. Shushan, et al., The
12.
Avis, I.M., M. Jett, T. Boyle, et al., Growth control of
determination of protein, oligonucleotide and peptide
lung cancer by interruption of 5-lipoxygenase-mediated
molecular weights by ion-spray mass spectrometry.
growth factor signaling. Journal of Clinical
Rapid Communications in Mass Spectrometry, 1988.
Investigation, 1996. 97(3): p. 806-13.
2(11): p. 249-56.
13.
Anderson, K.M., T. Seed, F. Ondrey, et al., The
31.
Chowdhury, S.K., V. Katta, and B.T. Chait, An
selective 5-lipoxygenase inhibitor A63162 reduces PC3
electrospray-ionization mass spectrometer with new
proliferation and initiates morphologic changes
features. Rapid Communications in Mass Spectrometry,
consistent with secretion. Anticancer Research, 1994.
1990. 4(3): p. 81-7.
14(5A): p. 1951-60.
32.
Smith, R.D., J.A. Loo, C.G. Edmonds, et al., New
14.
Ghosh, J. and C.E. Myers, Inhibition of arachidonate 5-
developments in biochemical mass spectrometry:
lipoxygenase triggers massive apoptosis in human
electrospray ionization. Analytical Chemistry, 1990.
prostate cancer cells. Proceedings of the National
62(9): p. 882-99.
Academy of Sciences of the United States of America,
33.
Nelson, M.J., D.B. Chase, and S.P. Seitz, Photolysis of
1998. 95(22): p. 13182-7.
"purple" lipoxygenase: implications for the structure of
15.
Tang, D.G. and K.V. Honn, 12-Lipoxygenase, 12(S)-
the chromophore. Biochemistry, 1995. 34(18): p. 6159-
HETE, and cancer metastasis. Annals of the New York
63.
Academy of Sciences, 1994. 744: p. 199-215.
34.
Wada, A., S. Ogo, Y. Watanabe, et al., Synthesis and
16.
Tang, D.G., I.M. Grossi, Y.Q. Chen, et al., 12(S)-HETE
Characterization of Novel Alkylperoxo Mononuclear
promotes tumor-cell adhesion by increasing surface
Iron(III) Complexes with Tripodal Pyridylamine
expression of alpha V beta 3 integrins on endothelial
Ligand: A Model for Peroxo Intermediates in Reactions
cells. International Journal of Cancer, 1993. 54(1): p.
Catalyzed by Non-Heme Iron Enzymes. Inorganic
102-11.
Chemistry, 1999. 38: p. 3592-3593.
17.
Honn, K.V., J. Timar, J. Rozhin, et al., A lipoxygenase
35.
Gorman, A.A., I. Hamblett, V.S. Srinivasan, et al.,
metabolite, 12-(S)-HETE, stimulates protein kinase C-
Curcumin-derived transients: a pulsed laser and pulse
mediated release of cathepsin B from malignant cells.
radiolysis study. Photochemistry & Photobiology,
Experimental Cell Research, 1994. 214(1): p. 120-30.
1994. 59(4): p. 389-98.
18.
Gao, X., D.J. Grignon, T. Chbihi, et al., Elevated 12-
36.
Chignell, C.F., P. Bilski, K.J. Reszka, et al., Spectral
lipoxygenase mRNA expression correlates with
and photochemical properties of curcumin.
advanced stage and poor differentiation of human
Photochemistry & Photobiology, 1994. 59(3): p. 295-
prostate cancer. Urology, 1995. 46(2): p. 227-37.
302.
2

---