Effect of carbohydrate moieties on the folate hydrolysis activity of the prostate specific membrane antigen
Effect of carbohydrate moieties on the folate hydrolysis activity of the prostate specific membrane antigen
复制标题
DOI：
10.1002/pros.10289
复制
发表时间：
2003-08-22
期刊：
影响因子：
2.8
通讯作者：
Heston, WDW
中科院分区：
文献类型：
--
作者：
Ghosh, A;Heston, WDW
背景前列腺特异性膜抗原（PSMA）是前列腺癌的重要细胞标志物之一，其表达在前列腺癌和其他肿瘤新生血管中增强许多倍。PSMA是一种II型膜糖蛋白，具有短的胞质N-末端区域、跨膜结构域和具有10个潜在N-连接糖基化位点的701个氨基酸的细胞外部分。PSMA是一种叶酸水解酶，其从聚谷氨酸和γ-谷氨酸化的叶酸裂解末端谷氨酸;以及NAALAD酶，其水解α-谷氨酸连接的二肽，N-乙酰基-乙酰基-谷氨酸（NAAG），并且是一种谷氨酸羧肽酶。在我们的研究中，我们已经使用各种酶或定点突变，以消除从PSMA蛋白的糖分子，并研究其叶酸水解酶的功能。我们对各种突变蛋白的N-连接糖基化进行了生化表征。结果。不同前列腺癌细胞系中表达的PSMA蛋白的糖基化差异。通过酶促或诱变去除糖残基可完全消除PSMA蛋白的酶活性。N-连接的碳水化合物结构对于蛋白质的叶酸水解酶功能是重要的。部分或完全去除糖会导致PSMA无酶活性，折叠不当，导致降解速率增加。(C)2003 Wiley-Liss，Inc.
BACKGROUND. Prostate specific membrane antigen or PSMA has been recognized as one of the important cellular markers for prostate cancer, the expression of which is enhanced many fold in prostate cancer and other tumor neovasculature. PSMA is a type II membrane glycoprotein with a short cytoplasmic N-terminal region, a transmembrane domain, and a 701 amino acid extracellular portion with 10 potential N-linked glycosylation sites. PSMA is a folate hydrolase, which cleaves terminal glutamates from poly- and gamma-glutamated folates; and NAALADase, which hydrolyses alpha-glutamate-linked dipeptide, N-acetyl-aspartyl-glutamate (NAAG) and is a glutamate carboxypeptidase.METHODS. In our study we have used various enzymes or site directed mutagenesis to remove sugar molecules from PSMA protein and studied its folate hydrolase function. We have performed a biochemical characterization of N-linked glycosylation of the various mutant proteins.RESULTS. PSMA protein expressed in different prostate cancer cell lines is differentially glycosylated. Removal of sugar residues either enzymatically or by mutagenesis abolishes the enzyme activity of PSMA protein completely.CONCLUSION. N-linked carbohydrate structures are important for the folate hydrolase function of the protein. Removal of sugars partially or completely causes PSMA to be enzymatically inactive, improperly folded, resulting in increased rate of degradation. (C) 2003 Wiley-Liss, Inc.