title: Leukotriene B4 omega-hydroxylase in human polymorphonuclear leukocytes. Suicidal inactivation by acetylenic fatty acids.
abstract: Human polymorphonuclear leukocytes (PMN) not only generate and respond to leukotriene B4 (LTB4), but also catabolize this mediator of inflammation rapidly and specifically by omega-oxidation (probably due to the action of a cytochrome P-450 enzyme). To develop pharmacologically useful inhibitors of the LTB4 omega-hydroxylase in human PMN, we devised a general scheme for synthesizing terminal acetylenic fatty acids based on the "acetylenic zipper" reaction. We found that the LTB4 omega-hydroxylase in intact PMN and in PMN sonicates is inactivated in a concentration-dependent fashion by terminal acetylenic analogues of lauric, palmitic, and stearic acids (i.e. 11-dodecynoic, 15-hexadecynoic, and 17-octadecynoic acids). Consistent with a suicidal process, inactivation of the LTB4 omega-hydroxylase requires molecular oxygen and NADPH, is time-dependent, and follows pseudo-first-order kinetics. Inactivation of the omega-hydroxylase by acetylenic fatty acids also is dependent on the terminal acetylenic moiety and the carbon chain length. Saturated fatty acids lacking a terminal acetylenic moiety do not inactivate the omega-hydroxylase. In addition, the two long-chain (C16, C18) acetylenic fatty acids inactivate the omega-hydroxylase at much lower concentrations (less than 5.0 microM) than those required for inactivation by the short-chain (C12) terminal acetylenic fatty acid (100 microM). Potent suicidal inhibitors of the LTB4 omega-hydroxylase in human PMN will help elucidate the roles played by LTB4 and its omega-oxidation products in regulating PMN function and in mediating inflammation.
mesh_terms: D000001:Calcimycin / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System; D000072470:Cytochrome P450 Family 4; D005227:Fatty Acids / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D007975:Leukotriene B4 / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000097:blood*; D009249:NADP / Q000494:pharmacology; D009504:Neutrophils / Q000201:enzymology*; D013329:Structure-Activity Relationship
chemical_list: D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D007975:Leukotriene B4; C047008:17-octadecynoic acid; D000001:Calcimycin; D009249:NADP; D003577:Cytochrome P-450 Enzyme System; C047007:15-hexadecynoic acid; D006899:Mixed Function Oxygenases; D000072470:Cytochrome P450 Family 4; C040780:leukotriene B4 20-hydroxylase