Glycoproteomics: Identifying the glycosylation of prostate specific antigen at normal and high isoelectric points by LC-MS/MS

Ehwang Song, Anoop Mayampurath, Chuan Yih Yu, Haixu Tang, Yehia Mechref

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

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.

Original languageEnglish
Pages (from-to)5570-5580
Number of pages11
JournalJournal of Proteome Research
Volume13
Issue number12
DOIs
StatePublished - Dec 5 2014

Keywords

  • LC-MS/MS
  • N-linked glycosylation
  • PSA
  • Prostate specific antigen
  • glycopeptide
  • glycoproteomics

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