Patterns for the y-Glutamyl Derivatives

Furthermore, in a very detailed investigation of the amino acid content of Beta vulgaris which permitted the identification of compounds present in extremely low concentrations only one y-glutamyl amino acid, y-glutamyl-y-aminobutyric acid, was found (54). 

As is apparent from the tables, most of the y-glutamyl derivatives have been found in seeds, although some have been identified in fresh plant parts. This is due partly to the fact that seeds have been more thoroughly investigated because of their availability and economic importance, but it also reflects the general tendency for non-protein amino acids and y-glutamyl derivatives to occur in high concentrations in seeds but in low concentrations or not at all in fresh plant parts (cf. Section VII. 5). 

Compound pKi (Shift in charge from +1 to 0) pK2 (Shift in charge from 0 to -1) Reference 

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). 

No CD- or ORD-measurements have been reported for y-glutamyl derivatives, but L-glutamine has a positive CD at 200 nm in H2O and at 208 nm in hydrochloric acid, similar to that of other simple a-L-amino acids (55). 

---