Rate limiting enzyme in bile acid synthesis ?
Ans. is 'c' i.e., 7a-hydroxylase About half of the cholesterol in the body is ultimately metabolized to bile acids. The primary bile acids are synthesized from cholesterol in liver. These are cholic acid and chenodeoxycholic acid. Rate limiting enzyme in primary bile acids synthesis is 7a - hydroxylase (cholesterol 7a - hydroxylase). This enzyme is inhibited by bile acids and induced by cholesterol. Thyroid hormones induce transcription of 7a-hydroxylase, thus in patients with hypothyroidism plasma cholesterol tends to rise (because of inhibition of 7a-hydroxylase which in turn inhibits conversion of cholesterol to bile acids).
Desmolase
21 a-hydroxylase
7a-hydroxylase
12a-hydroxylase