Effects of L-glutamyl peptides on the growth of L-glutamic acid crystals (alpha-form)

The effects of five gamma-L-glutamyl peptides, two alpha-L-glutamyl peptides, and L-phenylalanine (L-Phe) on the growth of {111} and {001} faces of the alpha-form of L-glutaminic acid (L-Glu) crystals were investigated. All the gamma-L-glutamyl and alpha-L-glutamyl peptides and L-Phe had inhibitory effects on the growth of the {111} face, but gamma-Glu-Glu, gamma-Glu-epsilon-Lys, and Glu-Glu suppressed not only the {111} faces but also the {001} faces. Thus, the distribution of additives on the {111} and {001} faces of L-Glu crystals was analyzed. Results showed that the {001} face of L-Glu crystals had higher concentrations of gamma-Glu-Glu, gamma-Glu-epsilon-Lys, and Glu-Glu than other peptides. The effect of gamma-Glu-Glu on inducing the beta-form is considered to be closely related to its specific character of inhibiting the growth of both the {111} and {001} faces of the alpha-form. These phenomena are discussed on the basis of the crystal structure.