Enzymatic Synthesis of γ‐Glutamyl Dipeptides Catalysed by Mutant E. coli γ‐Glutamyltransferases

Abstract

γ‐Glutamyltransferases (GGTs) from different sources have been proposed in recent times as biocatalysts for the enzymatic synthesis of naturally occurring γ‐glutamyl derivatives with flavor‐enhancer properties and interesting biological activities. Although the enzymatic approach is considered as a viable alternative to both the troublesome and low‐yielding extraction from natural sources and synthesis through peptide chemistry requiring protection/deprotection steps, yields are not completely satisfactory, due to the intervention of GGT‐catalysed hydrolysis and autotranspeptidation side‐reactions. Here, the design and the use as biocatalyst for preparative purposes of two mutants of E. coli GGT are described. The design of mutants was pursued by docking‐guided identification of residues putatively involved in interaction with the acceptor substrate, thus probably representing a first identification of residues constituting the still elusive and poorly characterized acceptor substrate binding site of the enzyme.