Song Ehwang, Mayampurath Anoop, Yu Chuan-Yih, Tang Haixu, Mechref Yehia
Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409, United States.
J Proteome Res. 2014 Dec 5;13(12):5570-80. doi: 10.1021/pr500575r. Epub 2014 Nov 10.
Prostate specific antigen (PSA) is currently used as a biomarker to diagnose prostate cancer. PSA testing has been widely used to detect and screen prostate cancer. However, in the diagnostic gray zone, the PSA test does not clearly distinguish between benign prostate hypertrophy and prostate cancer due to their overlap. To develop more specific and sensitive candidate biomarkers for prostate cancer, an in-depth understanding of the biochemical characteristics of PSA (such as glycosylation) is needed. PSA has a single glycosylation site at Asn69, with glycans constituting approximately 8% of the protein by weight. Here, we report the comprehensive identification and quantitation of N-glycans from two PSA isoforms using LC-MS/MS. There were 56 N-glycans associated with PSA, whereas 57 N-glycans were observed in the case of the PSA-high isoelectric point (pI) isoform (PSAH). Three sulfated/phosphorylated glycopeptides were detected, the identification of which was supported by tandem MS data. One of these sulfated/phosphorylated N-glycans, HexNAc5Hex4dHex1s/p1 was identified in both PSA and PSAH at relative intensities of 0.52 and 0.28%, respectively. Quantitatively, the variations were monitored between these two isoforms. Because we were one of the laboratories participating in the 2012 ABRF Glycoprotein Research Group (gPRG) study, those results were compared to that presented in this study. Our qualitative and quantitative results summarized here were comparable to those that were summarized in the interlaboratory study.
前列腺特异性抗原（PSA）目前被用作诊断前列腺癌的生物标志物。PSA检测已被广泛用于检测和筛查前列腺癌。然而，在诊断灰色区域，由于良性前列腺增生和前列腺癌存在重叠，PSA检测无法明确区分二者。为了开发更具特异性和敏感性的前列腺癌候选生物标志物，需要深入了解PSA的生化特性（如糖基化）。PSA在Asn69处有一个单一的糖基化位点，聚糖占蛋白质重量的约8%。在此，我们报告了使用液相色谱-串联质谱（LC-MS/MS）对两种PSA异构体的N-聚糖进行的全面鉴定和定量分析。与PSA相关的N-聚糖有56种，而在PSA高电荷异构体（PSAH）中观察到57种N-聚糖。检测到三种硫酸化/磷酸化糖肽，串联质谱数据支持了它们的鉴定。其中一种硫酸化/磷酸化N-聚糖，HexNAc5Hex4dHex1s/p1，在PSA和PSAH中均有鉴定，相对强度分别为0.52%和0.28%。在定量方面，监测了这两种异构体之间的差异。由于我们是参与2012年ABRF糖蛋白研究小组（gPRG）研究的实验室之一，将这些结果与本研究中的结果进行了比较。我们在此总结的定性和定量结果与实验室间研究中总结的结果相当。
