Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Department of Genetics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
Hum Mutat. 2020 Jan;41(1):133-139. doi: 10.1002/humu.23928. Epub 2019 Oct 14.
Mucolipidosis (ML) II and III alpha/beta are inherited lysosomal storage disorders caused by mutations in GNPTAB encoding the α/β-precursor of GlcNAc-1-phosphotransferase. This enzyme catalyzes the initial step in the modification of more than 70 lysosomal enzymes with mannose 6-phosphate residues to ensure their intracellular targeting to lysosomes. The so-called stealth domains in the α- and β-subunit of GlcNAc-1-phosphotransferase were thought to be involved in substrate recognition and/or catalysis. Here, we performed in silico alignment analysis of stealth domain-containing phosphotransferases and showed that the amino acid residues Glu , Asp , His , and Arg are highly conserved between different phosphotransferases. Interestingly, mutations in these residues were identified in patients with MLII and MLIII alpha/beta. To further support the in silico findings, we also provide experimental data demonstrating that these four amino acid residues are strictly required for GlcNAc-1-phosphotransferase activity and thus may be directly involved in the enzymatic catalysis.
黏脂贮积症（ML）II 和 III alpha/beta 是由 GNPTAB 基因突变引起的溶酶体贮积症，GNPTAB 编码 GlcNAc-1-磷酸转移酶的 α/β-前体。该酶催化超过 70 种溶酶体酶的甘露糖 6-磷酸残基的初始修饰步骤，以确保它们被靶向到溶酶体中。GlcNAc-1-磷酸转移酶的 α-和 β-亚基中的所谓“隐匿结构域”被认为参与了底物识别和/或催化。在这里，我们对含有隐匿结构域的磷酸转移酶进行了计算机序列比对分析，结果表明不同磷酸转移酶之间的氨基酸残基 Glu、Asp、His 和 Arg 高度保守。有趣的是，在 MLII 和 MLIII alpha/beta 患者中发现了这些残基的突变。为了进一步支持计算机分析结果，我们还提供了实验数据，证明这四个氨基酸残基是 GlcNAc-1-磷酸转移酶活性所必需的，因此可能直接参与酶催化。
