Identification and significance of the N-terminal part of swine pyruvate kinase in aged Parma hams

Within a project aimed at studying the peptide fraction in dry-cured Parma hams, a peptide was purified by means of reversed phase-high performance liquid chromatography (RP-HPLC) and identified by its molecular mass and amino acid sequence analysis. The peptide showed a very high degree of homology with the N-terminal part of different mammalian pyruvate kinases reported in databases and was accordingly identified as the N-terminal part of swine pyruvate kinase, whose sequence had never been reported before. The peptide was determined quantitatively by comparison with a suitable internal standard (Phe-Phe) in commercial ham samples with different age degrees. The peptide was found to be ubiquitous in Parma ham and its amount to increase during ageing even if a large variability was found within each assayed maturing time. The correlation found with the ham proteolysis degree (P<0.01) suggests that this peptide is related to the endopeptidasic activity. The peptide did not show a significant relationship with bitterness perception in assayed dry-cured ham, in agreement with the hypothesis that this taste is more related to free amino acids and low molecular weight peptides.