Enzymatic production of l-theanine by γ-glutamylmethylamide synthetase coupling with an ATP regeneration system based on polyphosphate kinase

Abstract

A process of l-theanine production by the recombinant γ-glutamylmethylamide synthetase (GMAS) coupled with an adenosine triphosphate (ATP) regeneration system that utilized inorganic polyphosphate (polyP) via polyphosphate kinase (PPK) was designed. The gmas gene from Methylovorus mays and ppk gene from Rhodobacter sphaeroides were cloned into pET-21a(+), then introduced into E. coli BL21(DE3) respectively. GMAS and PPK were both overexpressed in soluble forms. l-Theanine was efficiently produced from sodium glutamate, ethylamine hydrochloride and polyP with a very small amount of ATP. After 5h at 37°C and pH at 7.0, the 93% productivity of l-theanine was achieved at concentration of 200mM sodium glutamate and 200mM ethylamine hydrochloride with 5mM ATP. Productivity of l-theanine decreased to 84% when using 400mM sodium glutamate, and 26% when using 600mM sodium glutamate. The productivity of l-theanine obtained at a very small amount of ATP and high substrate concentration provides the basis for the large-scale industrial production of l-theanine.