Catalyzes the transfer of 2 methyl groups from 2 S-adenosyl-methionine molecules to the C-24 of lanosterol, producing first eburicol (24-methylenelanosterol) from lanosterol and then pneumocysterol (24Z-ethylidenelanosterol) from eburicol. lanosterol + S-adenosyl-L-methionine = eburicol + H(+) + S-adenosyl-L-homocysteine eburicol + S-adenosyl-L-methionine = (24Z)-ethylidenelanosterol + H(+) + S-adenosyl-L-homocysteine Optimum pH is 7.5. Optimum temperature is 37 degrees Celsius. Steroid metabolism. Cholesterol is the major sterol found in P.carinii, of which most, if not all, is scavenged from the host. In addition to cholesterol, 41 other sterols have been detected in P.carinii, but ergosterol, the major sterol in higher fungi, is not among them. Belongs to the class I-like SAM-binding methyltransferase superfamily. Erg6/SMT family.