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The covalent linkage of nonmeat proteins to myosin at temperatures and pH's common in meat product processing was investigated. Iodinated proteins were cross-linked to immobilized myosin and then quantitated by gamma counting after noncross-linked material was removed by washing with 6M guanidine hydrochloride. Bovine plasma transglutaminase catalyzed the formation of E-(y-glutamyl) lysine cross-links between myosin and soya protein, casein or gluten at 4-5°C for 16 hr and at pH's from 5.5-7.0. Casein was the best substrate with approximately 0.4g of casein cross-linked to l.Og myosin.

Collagenous peptides containing the Ehrlich chromogen (EC) were selectively isolated from a tryptic digest of bovine tendon by coupling to a diazotized polyacrylamide support. The isolated p-phenol-azo-EC peptides were purified and characterized by amino acid and sequence analyses. EC occurred in stoichiometric amounts in trimeric cross-linked chains originating from the known cross-link regions of type-I collagen. The major locus of the EC was alpha 2(I)Hyl-933 x alpha 1(I)Lys(Hyl)-9N x alpha 2(I)Lys(Hyl)-5N but it was also shown to occur at the loci alpha 1(I)Hyl-87 x alpha 1(I)Lys(Hyl)-16C x alpha 1(I)Lys(Hyl)-16C and alpha 1(I)Hyl-930 x alpha 1(I)Lys(Hyl)-9N x alpha 2(I)Lys(Hyl)-5N. After sequence analyses of the C-terminal helical cross-link region alpha 2(I)928-963, corrections are presented for residues 927, 930, 932 and 933 of the bovine alpha 2(I) chain. The collagen-associated EC is postulated to be a trisubstituted pyrrole formed by the reaction of the aldehyde form of a telopeptidyl lysine residue with a bifunctional keto amino cross-link. It is also proposed that when the telopeptidyl lysine residue is hydroxylated the above reaction will result in pyridinoline formation.

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