Different arrangement of epsilon(gamma-glutamyl)lysine cross-linking in Alaska pollock (Theragra chalcogramma) surimi proteins by Streptoverticilliumand endogenous transglutaminases during suwari process

The objective of the present study is to compare the protein cross-linking reaction in Alaska pollock surimi that is catalyzed by a commercially avail able microbial transglutaminase and by endogenous Alaska pollock transgluta minase. The endogenous transglutaminase was inhibited by EGTA and activated by CaCl2. The microbial transglutaminase was added to the salted surimi wi th and without EGTA and CaCl2. These surimi pastes were incubated at 25C up to 24 h followed by cooking at 90C. The resultant gels were fractionated i nto soluble and insoluble (aggregate) fractions by SDS-urea extraction. Com positional analysis revealed that the aggregate consisted predominantly of cross-linked myosin heavy chain. The distribution of epsilon-(gamma -glutam yl)lysine isopeptide in the soluble and aggregate fractions and peptide map ping analyses of the aggregate fraction demonstrate that the formation of i sopeptide cross-links in Alaska pollock surimi proteins during suwari proce ss differs when catalyzed by the microbial transglutaminase and endogenous transglutaminase.