Affinities of various mammalian arachidonate lipoxygenases and cyclooxygenases for molecular oxygen as substrate (original) (raw)
Related papers
European Journal of Biochemistry, 1993
When arachidonate 12-lipoxygenase purified from porcine leukocytes was incubated aerobically with 1-palmitoyl-2-arachidonoyl-~n-glycero-3-phosphocholine, the phospholipid reacted at up to 30% of the rate of a free fatty acid substrate; the esterified arachidonic acid was oxygenated predominantly to the (1 25')-12-hydroperoxy product. The porcine leukocyte enzyme was also capable of metabolizing phosphatidylcholine containing esterified (15s)-15-hydroperoxy-5,8,11,13-eicosatetraenoic acid ; oxygenation occurred predominantly at the 14R position. Reaction with mitochondrial and endoplasmic membranes of rat liver produced esterified (12S)-12-hydroperoxy-5,8,1O,lbeicosatetraenoic acid and (13S)-13-hydroperoxy-9,ll-octadecadienoic acid as major oxygenation products. Thus, porcine leukocyte 12-lipoxygenase is capable of oxygenating not only free polyenoic fatty acids but also more complex substrates such as phospholipids and biomembranes. In contrast, the human platelet 12-lipoxygenase is almost inactive with these esterified polyenoic fatty acids. In regard to the function of these enzymes, the leukocyte-type of 12-lipoxygenase has similar catalytic activities to the mammalian 15-lipoxygenase and its physiological function may include the structural modification of membrane lipids.
Inflammation, 1984
The effects of nordihydroguairetic acid (NDGA), 3-amino-1-trifluoromethyl-)-phenyl-2-pyrazoline (BW755c), eicostatetraynoic acid (ETYA), phenidone, quercetin, and indomethacin (INDO) on the synthesis of 15-hydroxyeicosatatetraenoic acid (15-HETE) from soybean 15-lipoxygenase, leukotriene B4 (LTB4 from 5-lipoxygenase, and prostaglandin E2 (PGE2 from cyclooxygenase enzymes of rat neutrophils and mouse peritoneal macrophages were investigated. All of the drugs caused a dose-related inhibition of increased oxygen consumption by soybean 15-lipoxygenase in the presence of arachidonic acid and the rank order of potency was phenidone ≥ BW755c > ETYA > quercetin > NDGA > indomethacin. The reduction in oxygen consumption correlated with a reduction of 15-HETE formation as identified by high-performance liquid chromatography. Apart from indomethacin, these drugs were also effective against the rat neutrophil 5-lipoxygenase, although the rank order of potency did not correlate with that obtained with soybean 15-lipoxygenase. Furthermore, in both A23187-activated rat neutrophils and zymosan-activated mouse peritoneal macrophages the synthesis of prostaglandins was inhibited by all of these drugs. In the neutrophils, the rank order of potency was INDO > ETYA > BW755c > quercetin > NDGA > phenidone, whereas in mouse peritoneal macrophages, the order was INDO > ETYA > BW755c > NDGA > quercetin > phenidone. These results suggest that putative lipoxygenase inhibitors exhibit both qualitative and quantitative differences in their effects on both lipoxygenases and cyclooxygenases.
FEBS Letters, 1983
Thromboxane Bz (TXB2) and 8,10,1Ceicosatetraenoic acid (12-HETE) formed from the endogenous and exogenous arachidonate during human platelet incubation, was evaluated by selected ion monitoring (SIM). TXBz formed from endogenous substrate accounted for about one third of the total, whereas the great part of 12-HETE derived from exogenous arachidonate. These data indicate that under the tested conditions the pool of arachidonate that acts as substrate for cycle-oxygenase is different from the pool that acts as substrate for lipoxygenase and that the arachidonate released from phospholipids is preferentially utilized by cycle-oxygenase.
Prostaglandins and Medicine, 1979
Biosynthesis of PG12, measured as 6-keto-PGFl,, thromboxane A2, measured as thromboxane B2, and prostaglandins E2, F c1 f and D2 by lymphocytes (WEHI-5), endothelial cells, normal human lung cells WI-38), normal human fibroblasts (D-550), rat adult Type II alveolar cells (L-2) and canine kidney cells (MDCK) was measured by radioimmunoassay of culture fluids before and after their separation by high pressure liquid chromatography. The metabolic profiles and the levels of each metabolite obtained by both procedures were comparable. The profile of arachidonic biosynthesis was unique to each cell. Endothelial cells synthesized primarily prostacyclin; the lymphocytes synthesized principally thromboxane. The dog kidney cells synthesized relatively large amounts of prostaglandin F20, I2 and E2, while the normal human lung cells produced predominantly prostaglandins E2, F2o, and thromboxane. The rat adult alveolar cell (L-2) and the normal human fibroblasts (D-550) biosynthesized primarily prostaglandins E2 and F2a.
Metabolism of arachidonate through NADPH-dependent oxygenase of renal cortex
Proceedings of the National Academy of Sciences, 1981
In normal kidneys the renal medulla very efficiently converts arachidonic acid to prostaglandins. Although the renal cortex has only trace amounts of cyclooxygenase activity, we report here the existence of an active cortical NADPH-dependent monooxygenase that converts arachidonate primarily into 19-hydroxy- and 20-hydroxyarachidonate as well as 19-ketoarachidonate and a dicarboxylic acid. The enzyme is presumably a cytochrome P-450 monooxygenase and demonstrated marked resistance to inhibition by 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF-525A), metyrapone, and carbon monoxide. In the rabbit kidney these products are produced only by the cortex in the presence of NADPH and represent the major metabolic products of arachidonate metabolism.
Annals of the New York Academy of Sciences, 1989
Arachidonic acid, the most abundant Go polyunsaturated fatty acid found in the phospholipids of mammalian tissues, is a biosynthetic precursor of several families of compounds that exert diverse biological effects. Once the action of phospholipases releases arachidonic acid from phospholipids, it is metabolized by one of the two pathways shown in FIGURE 1. The cyclooxygenase pathway produces prostaglandins (PG), thromboxanes (TX), and prostacyclins (PGI), whereas the lipoxygenase pathway leads to the formation of leukotrienes (LT) and lipoxins. The enzymic oxidation of arachidonic acid by way of the cyclooxygenase and lipoxygenase pathways to produce a spectrum of biologically active compounds is collectively referred to as the arachidonic acid cascade. Recent attention has focused on those factors that can regulate the concentration of these biologically active eicosanoids, especially in relation to their possible role in several pathological conditions including arteriosclerosis, arthritis, asthma, and anaphylactic reactions.'-3 One area of particular interest has been the effect of fatty acid hydroperoxides (FAHP) on lipoxygenase and cyclooxygenase activities. For example, both cyclooxygenase and lipoxygenase exhibit an obligatory requirement for FAHP ( < 1 pM) as an activator; however, these enzymes are inhibited by higher concentrations (> 10 pM) of FAHP."' The interest in FAHP, as modulators of the arachidonic acid cascade, probably reflects the implication of lipid peroxidation, one of the possible sources of FAHP formation, in many pathological and nonpathological in vivo processes.