Sterol 14alpha-demethylase that plays a critical role in the third module of ergosterol biosynthesis pathway, being ergosterol the major sterol component in fungal membranes that participates in a variety of functions ( , ). The third module or late pathway involves the ergosterol synthesis itself through consecutive reactions that mainly occur in the endoplasmic reticulum (ER) membrane (By similarity). In filamentous fungi, during the initial step of this module, lanosterol (lanosta-8,24-dien-3beta-ol) can be metabolized to eburicol (By similarity). Sterol 14alpha-demethylase catalyzes the three-step oxidative removal of the 14alpha-methyl group (C-32) of both these sterols in the form of formate, and converts eburicol and lanosterol to 14-demethyleburicol (4,4,24-trimethylergosta-8,14,24(28)-trienol) and 4,4-dimethyl-5alpha-cholesta-8,14,24-trien-3beta-ol, respectively, which are further metabolized by other enzymes in the pathway to ergosterol ( , ). Can also use substrates not intrinsic to fungi, such as 24,25-dihydrolanosterol (DHL), producing 4,4-dimethyl-8,14- cholestadien-3-beta-ol, but at lower rates than the endogenous substrates (By similarity).