Bile acids: Chemistry, physiology, and pathophysiology

Figure 3 Schematic representation of bile acid synthesis by the classical neutral pathway. AKR1C4: 3α-hydroxysteroid dehydrogenase; AKR1D1: Δ4–3-oxosteroid-5β-reductase; AMACR: Alpha methylacyl-CoA racemase; BAAT: Bile acid; CoA: Amino acid N-acyltransferase (¹A minor cytosolic fraction does also exist); BACS: Bile acid CoA synthetase; BCOX: Branched-chain acyl CoA oxidase; BDP: D-bifunctional protein hydratase; CYP27A1: Sterol 27-hydroxylase; CYP7A1: Cholesterol 7α-hydroxylase; CYP8B1: Sterol 12α-hydroxylase; HSD3B7: 3β-hydroxy-Δ5-C27-steroid dehydrogenase/isomerase; SCPx: Sterol carrier protein X; VLCS: Very long-chain acyl CoA synthetase; ER: Endoplasmic reticulum.