title: Adrenocortical cytochrome P-450 responsible for cholesterol side chain cleavage (P-450scc) is phosphorylated by the calcium-activated, phospholipid-sensitive protein kinase (protein kinase C).
abstract: Purified bovine adrenocortical cytochrome P-450scc (specific for cholesterol side chain cleavage in the inner mitochondrial membrane) was selectively phosphorylated in vitro by a Ca2+-activated, phospholipid-sensitive protein kinase (protein kinase C) preparation, whereas cyclic AMP dependent and two cyclic nucleotide independent kinases were ineffective. Cytochrome P-450scc incorporated a maximum of 4 mol of phosphate in the presence of protein kinase C within 15 min at 30 degrees C, with apparent Km and Vmax of 0.14 mumol and 0.76 pmol/min, respectively. Serine and threonine were the two target aminoacids phosphorylated in a ratio of about 1:1. In the presence of 1 microM Ca2+, a mixture of phosphatidylserine and diolein (or a potent tumor promoter phorbol ester) was required for optimal cytochrome P-450scc phosphorylation. In addition, purified inner mitochondrial membrane preparations from adrenocortical mitochondria were found to contain protein kinase C activity. These findings, together with the previous demonstration that activators of protein kinase C such as a potent phorbol ester activates steroidogenesis of intact adrenocortical cells, suggest that phosphorylation of P-450scc should be examined for its possible role in the regulation of adrenocortical functions.
mesh_terms: D000302:Adrenal Cortex / Q000201:enzymology*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000201:enzymology; D002122:Calcium Chloride / Q000494:pharmacology; D002417:Cattle; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology; D010088:Oxidoreductases / Q000378:metabolism*; D010718:Phosphatidylserines / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats
chemical_list: D000596:Amino Acids; D010718:Phosphatidylserines; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D002786:Cholesterol Side-Chain Cleavage Enzyme; D011494:Protein Kinases; D011493:Protein Kinase C; D002122:Calcium Chloride