FIGURE 1.

Schematic of the proposed cholesterol degradation pathway of Mtb. Key carbons of cholesterol are numbered using the steroid numbering convention. The processes of cholesterol side chain and partial ring degradation are shown as parallel pathways. Enzymes known to catalyze specific reactions in Mtb are indicated. Non-enzymatic reaction is shown as a dashed arrow. Compounds 1, 2, and 3 represent 4-AD, ADD, and 3-hydroxy-9,10-seconandrost-1,3,5(10)-trien-9,17-dione (3-HSA) (R = ketone); 4-BNC, 1,4-BNC, and 3-HSBNC, (R = isopropionate); 4-BNC-CoA, 1,4-BNC-CoA, and 3-HSBNC-CoA, (R = isopropionyl-CoA).