Deficiency of glucocerebrosidase (GBA), a lysosomal β-glucosidase, causes Gaucher disease. The enzyme hydrolyzes β-glucosidic substrates and transglucosylates cholesterol to cholesterol-β-glucoside. Here we show that recombinant human GBA also cleaves β-xylosides and transxylosylates cholesterol. The xylosyl-cholesterol formed acts as acceptor for subsequent formation of di-xylosyl-cholesterol. Common mutant forms of GBA from patients with Gaucher disease with reduced β-glucosidase activity were similarly impaired in β-xylosidase, transglucosidase and transxylosidase activities, except for a slightly reduced xylosidase/glucosidase activity ratio of N370S GBA and a slightly reduced transglucosylation/glucosidase activity ratio of D409H GBA. XylChol was found to be reduced in spleen from Gaucher disease patients. The origin of newly identified XylChol in mouse and human tissues was investigated. Cultured human cells exposed to exogenous β-xylosides generated XylChol in a manner dependent on active lysosomal GBA but not the cytosol-facing β-glucosidase GBA2. We later sought an endogenous β-xyloside acting as donor in transxylosylation reactions, identifying xylosylated ceramide (XylCer) in cells and tissues that serve as donor in the formation of XylChol. UDP-glucosylceramide synthase (GCS) was unable to synthesize XylChol but could catalyse formation of XylCer. Thus, food-derived β-D-xyloside and XylCer are potential donors for the GBA-mediated formation of XylChol in cells. The enzyme GCS produces XylCer at a low rate. Our findings point to further catalytic versatility of GBA and prompt a systematic exploration of the distribution and role of xylosylated lipids.

中文翻译：

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人葡萄糖脑苷脂酶通过 β-木糖苷酶和转木糖苷酶反应介导木糖酰胆固醇的形成。


葡萄糖脑苷脂酶 (GBA)（一种溶酶体 β-葡萄糖苷酶）缺乏会导致戈谢病。该酶水解 β-葡萄糖苷底物并将胆固醇转葡糖基化为胆固醇-β-葡萄糖苷。在这里，我们证明重组人 GBA 还可以裂解 β-木糖苷并转木糖基化胆固醇。形成的木糖基胆固醇充当随后形成二木糖基胆固醇的受体。 β-葡萄糖苷酶活性降低的戈谢病患者的常见 GBA 突变形式的 β-木糖苷酶、转葡萄糖苷酶和转木糖苷酶活性同样受损，但 N370S GBA 的木糖苷酶/葡萄糖苷酶活性比略有降低，转葡萄糖基化/葡萄糖苷酶活性也略有降低D409H GBA 的比率。研究发现戈谢病患者脾脏中的木胆胆减少。研究了小鼠和人体组织中新鉴定的 XylChol 的起源。暴露于外源 β-木糖苷的培养人类细胞以依赖于活性溶酶体 GBA 而不是面向细胞质的 β-葡萄糖苷酶 GBA2 的方式产生 XylChol。后来，我们寻找一种内源性 β-木糖苷作为转木糖基反应中的供体，并鉴定出细胞和组织中的木糖基化神经酰胺 (XylCer) 在木胆胆的形成中充当供体。 UDP-葡萄糖神经酰胺合酶（GCS）不能合成XylChol，但可以催化XylCer的形成。因此，食物来源的 β-D-木糖苷和 XylCer 是细胞中 GBA 介导的 XylChol 形成的潜在供体。 GCS 酶以低速率产生 XylCer。我们的研究结果表明 GBA 具有进一步的催化多功能性，并促进对木糖化脂质的分布和作用的系统探索。