Scheme 1. Cholesterol Side Chain Metabolism in Mycobacterium tuberculosis.

Cyp125 initiates cholesterol side chain degradation.¹⁰⁻¹² FadD19 acyl-CoA ligase activates the resultant steroid carboxylic acid through esterification with CoA.¹³ The steroid side chain is truncated via three cycles of β-oxidation to yield one acetyl-CoA and two propionyl-CoA’s (highlighted in purple) and androstendione. The first step in each β-oxidation cycle is labeled with the acyl-CoA dehydrogenase that catalyzes the oxidation and highlighted in blue text. The bonds undergoing modification are highlighted in red. Additional steps are labeled with specific enzyme names, if known.