Y-Glutamyl linkage

Rotations at the sodium o-Iine for the majority of the y-glutamyl derivatives in either water or hydrochloric acid have been reported. Although the y-glutamyl linkage is unstable towards acid (see Section IV. 9), it is possible to obtain reliable rotations for hydrochloric acid solutions if the rotation is measured within 5 min of the preparation of the solution furthermore, one can check that no measurable change in rotation takes place in the first 15 min. The rotation of glutamine itself has previously been determined under these conditions 218). 

Several reviews are available on the synthesis of peptides containing y-glutamyl linkages [see for example Ref. (78), p. 1093, (117, 313, 553)]. Whereas considerable ingenuity has been used in developing new syntheses of y-glutamyl derivatives, nearly all syntheses of the compounds described in the present review employed one of five standard methods, all of which have proven dependable even in the hands of workers who are not specially trained in peptide synthesis. 

This enzyme [EC 3.4.19.5], now known as /3-aspartyl-peptidase, is a mammahan cytosolic protein that catalyzes the hydrolysis of a /3-hnked aspartyl residue from the N-terminus of a polypeptide. Other isopeptide linkages (e.g., a y-glutamyl hnkage) are not hydrolyzed by this enzyme. 

C. y-Glutamyl and /8-Aspartyl Peptide Linkages Proteins, Especially Collagen and Gelatin. ... 

Factor XIII will slowly form c-N- (y-glutamyl) lysine cross-linkages in fibrinogen, in itself and in other proteins (37). Transaminases from other sources will also cross-link fibrin, as well as other proteins. In addition, they will covalently attach amino-containing substrates to the y-carboxyl group of glutamic acid residues in proteins (38). 

---