Immobilization of γ-glutamyl transpeptidase from equine kidney for the synthesis of kokumi peptides

Kokumi is a Japanese term that refers to taste perception defined as having mouthfulness, thickness and a long-lasting savory sensation. Although being nearly tasteless in themselves, kokumi compounds are able to elicit strong taste sensations, especially when associated with protein-rich food, thus acting as true flavor enhancers. Kokumi compounds in nature are mainly γ-glutamyl derivatives of amino acids or modified amino acids [1]. Despite their relatively simple chemical structure, the synthesis of γ-glutamyl derivatives through the classical peptide chemistry is not straightforward due to the need of protection and deprotection steps. Therefore, an enzymatic approach can represent an appealing solution for their supply. γ-Glutamyl transpeptidase (GGT, E.C. 2.3.2.2) is a an intrinsic membrane enzyme which transfers the γ-glutamyl moiety of glutathione to acceptors producing γ-glutamyl derivatives [2,3]. In this context, an immobilization study of the GGT from equine kidney (ekGGT) [4] was performed with the aim to develop a robust biocatalyst for the synthesis of γ-glutamyl derivatives of industrial relevance. Different binding chemistry and chemical activation of the support as well as reaction conditions were assayed to set up a tailor-made immobilization protocol. Octyl/glyoxyl heterofunctional agarose [5] resulted in a high immobilization yield and a good activity recovery.