title: C21 steroid side chain cleavage enzyme from porcine adrenal microsomes. Purification and characterization of the 17 alpha-hydroxylase/C17,20-lyase cytochrome P-450.
abstract: The properties and the purity of a cytochrome P-450 (17 alpha-hydroxylase) from porcine adrenal microsomes have been examined following a report that the corresponding enzyme from bovine adrenocortical microsomes is inactive as a 17 alpha-hydroxylase and fails to show a high spin spectrum on addition of substrate, once the enzyme has been purified (Bumpus, J. A., and Dus, K. M. (1982) J. Biol. Chem. 257, 12696-12704). The purity of the porcine enzyme was demonstrated by electrophoresis on polyacrylamide with sodium dodecyl sulfate, immunoelectrophoresis, and NH2-terminal amino acid sequence (16 residues). The pure enzyme shows Mr = 54,000, heme content of greater than 0.8 nmol/nmol of protein, and absorption spectra typical of cytochrome P-450. The enzyme is active with both delta 4 (progesterone) and delta 5 (pregnenolone) substrates as a 17 alpha-hydroxylase and with the corresponding 17 alpha-hydroxysteroids as a C17,20-lyase. All four substrates produce typical type I spectra with the enzyme (so-called high spin form). We conclude that: 1) porcine adrenal microsomes contain a 17 alpha-hydroxylase/C17,20-lyase which is a single protein molecule readily purified to an enzymatically active form; 2) the C17,20-lyase activity is largely suppressed in the microsomes; and 3) the enzyme closely resembles that found in testicular microsomes. We propose that this enzyme be referred to as the adrenal C21 steroid side chain cleavage enzyme.
mesh_terms: D000311:Adrenal Glands / Q000201:enzymology*; D000446:Aldehyde-Lyases / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D013053:Spectrophotometry; D013254:Steroid 17-alpha-Hydroxylase / Q000302:isolation & purification / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013552:Swine
chemical_list: D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D013254:Steroid 17-alpha-Hydroxylase; D002786:Cholesterol Side-Chain Cleavage Enzyme; D000446:Aldehyde-Lyases