Involved in the utilization of cholesterol as the sole carbon and energy source by degrading the side chain during infection (PubMed:20843794, PubMed:20545858). Primarily catalyzes the sequential oxidation of the terminal methyl of cholest-4-en-3-one into (25S)-26-hydroxycholest-4-en-3-one (alcohol), (25S)-26-oxocholest-4-en-3-one (aldehyde), to finally yield the carboxylic acid (25S)-3-oxocholest-4-en-26-oate (PubMed:19846551, PubMed:20843794, PubMed:20545858). Also able to sequentially oxidize cholesterol itself, not only cholest-4-en-3-one (PubMed:19846551, PubMed:20843794, PubMed:20545858). cholest-4-en-3-one + 5 H(+) + 3 O2 + 6 reduced [2Fe-2S]-[ferredoxin] = (25S)-3-oxocholest-4-en-26-oate + 4 H2O + 6 oxidized [2Fe-2S]-[ferredoxin] (25R)-3-oxocholest-4-en-26-ol + 2 H(+) + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = (25R)-3-oxocholest-4-en-26-al + 2 H2O + 2 oxidized [2Fe-2S]-[ferredoxin] (25R)-3-oxocholest-4-en-26-al + H(+) + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = (25R)-3-oxocholest-4-en-26-oate + H2O + 2 oxidized [2Fe-2S]-[ferredoxin] cholest-4-en-3-one + 2 H(+) + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = (25S)-3-oxocholest-4-en-26-ol + H2O + 2 oxidized [2Fe-2S]-[ferredoxin] (25S)-3-oxocholest-4-en-26-ol + 2 H(+) + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = (25S)-3-oxocholest-4-en-26-al + 2 H2O + 2 oxidized [2Fe-2S]-[ferredoxin] (25S)-3-oxocholest-4-en-26-al + H(+) + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = (25S)-3-oxocholest-4-en-26-oate + H2O + 2 oxidized [2Fe-2S]-[ferredoxin] Steroid metabolism; cholesterol degradation. By cholesterol. Cells lacking this gene appear to metabolize cholesterol normally, probably due to the ability of Cyp142 to compensate for loss of Cyp125. Belongs to the cytochrome P450 family.