Regulation of hydroxylations in biosynthesis of bile acids: modulation of reconstituted 12 alpha-hydroxylase activity by protein fractions from rabbit liver cytosol and microsomes.
The activity of purified 12 alpha-hydroxylase from rabbit liver microsomes was modulated by including protein fractions from rabbit liver microsomes and cytosol into the system. The microsomal protein fraction stimulated 12 alpha-hydroxylation two times. The cytosolic fraction inhibited the reaction markedly. The microsomal 12 alpha-hydroxylase stimulatory activity was labile and the cytosolic 12 alpha-hydroxylase inhibitory activity was stable to mild heat treatment. Addition of ATP and MgCl2 or NaF had no effect on the activities of the two protein fractions. The activity of the microsomal stimulatory fraction decreased upon storage but could be reactivated by addition of reduced glutathione to the system.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003600:Cytosol / Q000032:analysis; D005978:Glutathione / Q000494:pharmacology; D006900:Hydroxylation; D008099:Liver / Q000032:analysis*; D008274:Magnesium / Q000494:pharmacology; D008862:Microsomes, Liver / Q000032:analysis; D011506:Proteins / Q000302:isolation & purification*; D011817:Rabbits; D012969:Sodium Fluoride / Q000494:pharmacology; D013253:Steroid 12-alpha-Hydroxylase / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*
D001647:Bile Acids and Salts; D011506:Proteins; D000255:Adenosine Triphosphate; D012969:Sodium Fluoride; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C038211:7-hydroxycholesterol-12-alpha-hydroxylase; D013253:Steroid 12-alpha-Hydroxylase; D005978:Glutathione; D008274:Magnesium