Molecular Glycobiology, Research Team for Mechanism of Aging, Tokyo Metropolitan Institute of Gerontology, Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, 35-2 Sakaecho, Tokyo 173-0015, Japan.
Biochem Biophys Res Commun. 2011 Jul 8;410(3):632-6. doi: 10.1016/j.bbrc.2011.06.042. Epub 2011 Jun 13.
Protein O-linked mannose β1,2-N-acetylglucosaminyltransferase 1 (POMGnT1) catalyzes the transfer of GlcNAc to O-mannose of glycoproteins. Mutations in the POMGnT1 gene cause muscle-eye-brain disease (MEB). POMGnT1 is a typical type II membrane protein, which is localized in the Golgi apparatus. However, details of the catalytic and reaction mechanism of POMGnT1 are not understood. To develop a better understanding of POMGnT1, we examined the substrate specificity of POMGnT1 using a series of synthetic O-mannosyl peptides based on the human α-dystroglycan (α-DG) sequence as substrates. O-Mannosyl peptides consisting of three to 20 amino acids are recognized as substrates. Enzyme kinetics improved with increasing peptide length up to a length of 8 amino acids but the kinetics of peptides longer than 8 amino acids were similar to those of octapeptides. Our results also show that the amino acid sequence affects POMGnT1 activity. These data suggest that both length and amino acid sequence of mannosyl peptides are determinants of POMGnT1 substrate specificity.
蛋白 O-连接甘露糖β1,2-N-乙酰氨基葡萄糖基转移酶 1（POMGnT1）催化糖蛋白 O-甘露糖上的 GlcNAc 转移。POMGnT1 基因的突变会导致肌肉眼脑疾病（MEB）。POMGnT1 是一种典型的 II 型膜蛋白，定位于高尔基体。然而，POMGnT1 的催化和反应机制的细节尚不清楚。为了更好地了解 POMGnT1，我们使用一系列基于人α- dystroglycan（α-DG）序列的合成 O-甘露糖肽作为底物来研究 POMGnT1 的底物特异性。三到二十个氨基酸组成的 O-甘露糖肽被认为是底物。随着肽长度的增加，酶动力学得到改善，最长可达 8 个氨基酸，但长度大于 8 个氨基酸的肽的动力学与八肽的动力学相似。我们的结果还表明，氨基酸序列会影响 POMGnT1 的活性。这些数据表明，甘露糖肽的长度和氨基酸序列都是 POMGnT1 底物特异性的决定因素。
