Sterylglucosides (SGs) are composed of a glucose and sterol derivatives, and are distributed in fungi, plants and mammals. We recently identified EGCrP1 and EGCrP2 (endoglycoceramidase-related proteins 1 and 2) as a β-glucocerebrosidase and steryl-β-glucosidase, respectively, in Cryptococcus neoformans. We herein describe an EGCrP2 homologue (Egh1; ORF name, Yir007w) involved in SG catabolism in Saccharomyces cerevisiae. The purified recombinant Egh1 hydrolyzed various β-glucosides including ergosteryl β-glucoside (EG), cholesteryl β-glucoside, sitosteryl β-glucoside, para-nitrophenyl β-glucoside, 4-methylumberifellyl β-glucoside and glucosylceramide. The disruption of EGH1 in S. cerevisiae BY4741 (egh1Δ) resulted in the accumulation of EG and fragmentation of vacuoles. The expression of EGH1 in egh1Δ (revertant) reduced the accumulation of EG, and restored the morphology of vacuoles. The accumulation of EG was not detected in EGH1 and UGT51(ATG26) double-disrupted mutants (ugt51Δegh1Δ), indicating that EG was synthesized by Ugt51(Atg26) and degraded by Egh1 in vivo. These results clearly demonstrated that Egh1 is an ergosteryl-β-glucosidase that is functionally involved in the EG catabolic pathway and vacuole formation in S. cerevisiae.
甾基
葡糖苷(SGs)由
葡萄糖和
甾醇衍
生物组成,分布于真菌、植物和哺乳动物中。我们最近发现
EGCrP1 和
EGCrP2(内糖糖苷酶相关蛋白 1 和 2)分别是新隐球菌中的β-
葡糖脑苷脂和甾基-β-
葡糖苷酶。我们在此描述了参与酿酒酵母中 SG 分解代谢的
EGCrP2 同源物(
EGh1;ORF 名称 Yir007w)。纯化的
重组 EGh1 可
水解各种 β-
葡萄糖苷,包括麦角甾基 β-
葡萄糖苷(
EG)、
胆固醇基 β-
葡萄糖苷、西
固醇基 β-
葡萄糖苷、对
硝基苯基 β-
葡萄糖苷、4-甲基贝壳杉基 β-
葡萄糖苷和
葡萄糖酰胺。在 S. cerevisiae BY4741(
EGh1Δ)中破坏
EGH1 会导致
EG 积累和液泡破碎。在
EGh1Δ(还原型)中表达
EGH1 可减少
EG 的积累,并恢复液泡的形态。在
EGH1和UGT51(ATG26)双中断突变体(ugt51Δ
EGh1Δ)中未检测到
EG的积累,表明
EG在体内由Ugt51(Atg26)合成并由
EGh1降解。这些结果清楚地表明,
EGh1 是一种
麦角固醇基-β-
葡萄糖苷酶,在功能上参与了 S. cerevisiae 的
EG 分解途径和液泡形成。