Maeda Y, Tanaka S, Hino J, Kangawa K, Kinoshita T
Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
EMBO J. 2000 Jun 1;19(11):2475-82. doi: 10.1093/emboj/19.11.2475.
Dolichol-phosphate-mannose (DPM) synthase generates mannosyl donors for glycosylphosphatidylinositols, N-glycan and protein O- and C-mannosylation. In Saccharomyces cerevisiae, this enzyme is encoded by DPM1. We reported previously that mammalian DPM synthase contains catalytic DPM1 and regulatory DPM2 subunits, and that DPM1 requires DPM2 for its stable expression in the endoplasmic reticulum. Here we report that human DPM synthase consists of three subunits. The third subunit, DPM3, comprises 92 amino acids associated with DPM1 via its C-terminal domain and with DPM2 via its N-terminal portion. The stability of DPM3 was dependent upon DPM2. However, overexpression of DPM3 in Lec15 cells, a null mutant of DPM2, restored the biosynthesis of DPM with an increase in DPM1, indicating that DPM3 directly stabilized DPM1. Therefore, DPM2 stabilizes DPM3 and DPM3 stabilizes DPM1. DPM synthase activity was 10 times higher in the presence of DPM2, indicating that DPM2 also plays a role in the enzymatic reaction. Schizosaccharomyces pombe has proteins that resemble three human subunits; S.pombe DPM3 restored biosynthesis of DPM in Lec15 cells, indicating its orthologous relationship to human DPM3.
多萜醇磷酸甘露糖（DPM）合酶可生成用于糖基磷脂酰肌醇、N-聚糖以及蛋白质O-甘露糖基化和C-甘露糖基化的甘露糖基供体。在酿酒酵母中，该酶由DPM1编码。我们之前报道过，哺乳动物DPM合酶包含催化性的DPM1和调节性的DPM2亚基，并且DPM1在内质网中稳定表达需要DPM2。在此我们报道，人DPM合酶由三个亚基组成。第三个亚基DPM3由92个氨基酸组成，其通过C端结构域与DPM1相连，并通过N端部分与DPM2相连。DPM3的稳定性取决于DPM2。然而，在DPM2基因敲除突变体Lec15细胞中过表达DPM3可恢复DPM的生物合成，同时DPM1增加，这表明DPM3可直接稳定DPM1。因此，DPM2稳定DPM3，而DPM3稳定DPM1。在有DPM2存在的情况下，DPM合酶活性提高了10倍，这表明DPM2在酶促反应中也发挥作用。粟酒裂殖酵母具有与人类三个亚基相似的蛋白质；粟酒裂殖酵母DPM3可恢复Lec15细胞中DPM的生物合成，表明其与人类DPM3具有直系同源关系。
