Investigation of the substrate specificity of glutamyl endopeptidase using purified bovine β-casein and synthetic peptides

Phanindra Kalyankar, Yishen Zhu, Gerard O'Cuinn, Richard J. Fitzgerald

Research output: Contribution to journalArticlepeer-review

Abstract

Purified bovine β-casein was digested with glutamyl endopeptidase (GE) at 37 and 50 C for 4 h. The peptides generated were determined using nano-LC-ESI-qTOF-MS/MS. GE was highly specific and hydrolyzed peptide bonds in β-casein predominantly on the carboxy terminal of Glu and Asp. Pro residues were not preferred, while Met was poorly preferred at the P1′ position. Glu-Met hydrolysis was less preferred in comparison to Asp-Met hydrolysis. Five synthetic peptides corresponding to specific sequences in β-casein were incubated with GE at 37 C to further characterize the substrate specificity. MS analysis of the digestion products indicated that GE hydrolyzed Glu-Ser in Glu-Glu-Ser. Furthermore, hydrolysis of Glu-Met and Glu-Pro was observed. The presence of multiple-phosphorylated Ser residues upstream from the scissile bond did not appear to affect hydrolysis of Glu-Ser. The results herein are relevant to our understanding of the substrate specificity of GE and the peptides that may be expected during the hydrolysis of β-casein.

Original languageEnglish
Pages (from-to)3193-3204
Number of pages12
JournalJournal of Agricultural and Food Chemistry
Volume61
Issue number13
DOIs
Publication statusPublished - 3 Apr 2013

Keywords

  • bovine β-casein
  • glutamyl endopeptidase
  • LC-MS/MS
  • substrate specificity
  • synthetic peptides

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