An overview of the phytosterol degradation pathway in Mycobacterium HGMS2. Each steroid intermediate is numbered. Open arrows refer to a known pathway for the accumulation of 4-AD (S5) and solid lines refer to the ring-broken reactions. Dashed lines refer to unknown pathways to accumulate BA (S11) and 3-OPCM (S13). The information on all steroid intermediates is summarized in Table 2