De novo biosynthesis of purine nucleotides (Saccharomyces cerevisiae)

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The ergosterol biosynthesis pathway is required for generation of a major constituent of the fungal plasma membrane, ergosterol (CITS: [Paltauf])(CITS: [8561481]). This pathway is fungal-specific; plasma membranes of other organisms are composed predominantly of other types of sterol. However, the pathway is not universally present in fungi; for example, Pneumocystis carinii plasma membranes lack ergosterol (CITS: [12531182]). In S. cerevisiae, some steps in the pathway are dispensible while others are essential for viability (CITS: [8277826]). The ergosterol biosynthesis pathway has been the subject of intensive investigation as a target of antifungal drugs (CITS: [11815273]). The major target of azole antifungal drugs is lanosterol 14-alpha demethylase, a member of the cytochrome P450 family known as Erg11 protein in many fungal species. Squalene epoxidase (Erg1p in S. cerevisiae) is the specific target of allylamine drugs such as terbinafine (CITS: [14638499]). Mutations in the genes encoding these enzymes and others in the pathway, as well as alterations in the expression levels of the pathway constituents, can lead to antifungal drug resistance (CITS: [11815273]). SOURCE: SGD pathways, http://pathway.yeastgenome.org/server.html

GenMAPP remarks 

Based on http://pathway.yeastgenome.org/biocyc/