Prostaglandin and fatty acid omega- and (omega-1)-oxidation in rabbit lung. Acetylenic fatty acid mechanism-based inactivators as specific inhibitors.
Terminal acetylenic fatty acid mechanism-based inhibitors (Ortiz de Montellano, P. R., and Reich, N. O. (1984) J. Biol. Chem. 259, 4136-4141) were used as probes in determining the substrate specificity of rabbit lung cytochrome P-450 isozymes of pregnant animals in both microsomes and reconstituted systems. Lung microsomal and reconstituted P-450 form 5-catalyzed lauric acid omega- and (omega-1)-hydroxylase activities were inhibited by a 12-carbon terminal acetylenic fatty acid, 11-dodecynoic acid (11-DDYA), and an 18-carbon terminal acetylenic fatty acid, 17-octadecynoic acid (17-ODYA). Rabbit lung microsomal lauric acid omega-hydroxylase activity was more sensitive to inhibition by 11-DDYA than was (omega-1)-hydroxylase activity. In reconstituted systems containing purified P-450 form 5, both omega- and (omega-1)-hydroxylation of lauric acid were inhibited in parallel when either 11-DDYA or 17-ODYA was used. These data suggest the presence of at least two P-450 isozymes in rabbit lung microsomes capable of lauric acid omega-hydroxylation. This is the first report indicating the multiplicity of lauric acid hydroxylases in lung microsomes. Lung microsomal prostaglandin omega-hydroxylation, mediated by the pregnancy-inducible P-450PG-omega (Williams, D. E., Hale, S. E., Okita, R. T., and Masters, B. S. S. (1984) J. Biol. Chem. 259, 14600-14608) was subject to inhibition by 17-ODYA only, whereas 11-DDYA acid was not an effective inhibitor of this hydroxylase. We have recently developed a new terminal acetylenic fatty acid, 12-hydroxy-16-heptadecynoic acid (12-HHDYA), that contains a hydroxyl group at the omega-6 position. We show that 12-HHDYA possesses a high degree of selectivity for the inactivation of rabbit lung microsomal prostaglandin omega-hydroxylase activity which cannot be obtained with the long chain acetylenic inhibitor, 17-ODYA. In addition, 12-HHDYA has no effect on lauric acid omega- or omega-1-hydroxylation or on benzphetamine N-demethylation. The development of this new terminal acetylenic fatty acid inhibitor provides us with a useful tool with which to study the physiological role of prostaglandin omega-hydroxylation in the rabbit lung during pregnancy.
Muerhoff
A S
AS
Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226.
Williams
D E
DE
Reich
N O
NO
CaJacob
C A
CA
Ortiz de Montellano
P R
PR
Masters
B S
BS
D000818:Animals; D042926:Cytochrome P-450 CYP4A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D007850:Lauric Acids / Q000378:metabolism*; D008168:Lung / Q000201:enzymology*; D008861:Microsomes / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors*; D011454:Prostaglandins A / Q000378:metabolism*; D011817:Rabbits
D005231:Fatty Acids, Unsaturated; D007527:Isoenzymes; D007850:Lauric Acids; D011454:Prostaglandins A; C030358:lauric acid; C040948:11-dodecynoic acid; C047008:17-octadecynoic acid; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D042926:Cytochrome P-450 CYP4A; D015232:Dinoprostone; C100573:prostaglandin A1