Multiple forms of cytochrome P-450 in rabbit colon microsomes.
Three cytochrome P-450 preparations, designated as cytochrome P-450ca, cytochrome P-450cb, and cytochrome P-448c fraction, were separated and purified about 23-, 50-, and 29-fold, respectively, from the cholate extracts of rabbit colon mucosa microsomes. Their specific contents were 1.2, 2.6, and 1.5 nmol of cytochrome P-450 per mg of protein, respectively. Cytochrome P-450ca and cytochrome P-450cb migrated as heme-containing polypeptide bands with molecular weights of about 53,000 and 57,000, respectively, on SDS-polyacrylamide gel electrophoresis. The CO-reduced difference spectra of cytochrome P-450ca, cytochrome P-450cb, and cytochrome P-448c fraction showed maxima at 451, 450, and 449 nm, respectively. Cytochrome P-450ca efficiently catalyzed the omega-hydroxylation of prostaglandin A1 (PGA1) and the omega- and (omega-1)-hydroxylation of caprate, laurate, and myristate in the reconstituted system containing cytochrome P-450ca, NADPH-cytochrome P-450 reductase, cytochrome b5, and phosphatidylcholine. In contrast, cytochrome P-450cb and cytochrome P-448c fraction had no detectable activity toward PGA1 and fatty acids. Both catalyzed aminopyrine and benzphetamine N-demethylation. Cytochrome P-448c fraction also hydroxylated benzo(a)pyrene, and phosphatidylinositol or phosphatidylserine exhibited a stimulatory effect on this activity. The results show that rabbit colon microsomes contain catalytically different cytochrome P-450, one of which is specialized for the omega-oxidation prostaglandins, the others being involved in the metabolism of exogenous compounds such as drugs and polycyclic hydrocarbons.
D000818:Animals; D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D003106:Colon / Q000201:enzymology*; D019388:Cytochrome P-450 CYP1A2; D003577:Cytochrome P-450 Enzyme System / Q000145:classification / Q000302:isolation & purification*; D003580:Cytochromes / Q000302:isolation & purification; D006868:Hydrolysis; D007413:Intestinal Mucosa / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D011817:Rabbits; D013053:Spectrophotometry
D003580:Cytochromes; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C017170:Cyp1a2 protein, rat; D019388:Cytochrome P-450 CYP1A2; C026961:prostaglandin omega hydroxylases