γ-Glutamyl compounds and their enzymatic production using bacterial γ-glutamyltranspeptidase

Summary.

Some amino acids and peptides, which have low solubility in water, become much more soluble following γ-glutamylation. Compounds become more stable in the blood stream with γ-glutamylation. Several γ-glutamyl compounds are known to have favorable physiological effects on mammals. γ-Glutamylation can improve taste and can stabilize glutamine in aqueous solution. Because of such favorable features, γ-glutamyl compounds are very attractive. However, only a small number of γ-glutamyl amino acids have been studied although many other γ-glutamyl compounds may have characteristics that will benefit humans. This is mainly because γ-glutamyl compounds have not been readily available. An efficient and simple method of producing various γ-glutamyl compounds, especially γ-glutamyl amino acids, using bacterial γ-glutamyltranspeptidase has been developed. With this method, modifications of reactive groups of the substrate and energy source such as ATP are not required, and a wide-range of γ-glutamyl compounds can be synthesized. Moreover, bacterial γ-glutamyltranspeptidase, a catalyst for this method, is readily available from the strain over-producing this enzyme. The superiority of producing γ-glutamyl compounds with bacterial γ-glutamyltranspeptidase over other methods of production is discussed.