title: Purification of cytochrome P-450 catalyzing 25-hydroxylation of vitamin D3 from rat liver microsomes.
abstract: Cytochrome P-450 catalyzing 25-hydroxylation of cholecalciferol (cytochrome P-450 cc25 ) was purified from rat liver microsomes based on its catalytic activity at each purification step. The specific cytochrome P-450 content of the final preparation was 15.1 nmol/mg of protein. Reconstituted activity of 25-hydroxylation of cholecalciferol with the purified enzyme was 2.3 nmol/min/mg of protein, which was 4,300 times as high as that in microsomes. The minimum molecular weight of the enzyme was 50,000 based on SDS-polyacrylamide gel electrophoretogram. Amino terminal sequence of the P-450 cc25 was H2N-Met-Asp-Pro-Val-Leu-Val-. Immunochemical study showed that the purified P-450 cc25 was homogeneous and the cytochrome was immunochemically different from either cytochrome P-450(PB-1) or cytochrome P-448(MC-1).
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D053493:Cholestanetriol 26-Monooxygenase; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005779:Immunodiffusion; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013250:Steroid Hydroxylases / Q000378:metabolism*
chemical_list: D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D053493:Cholestanetriol 26-Monooxygenase