Purification and properties of gamma-glutamyl transpeptidase from Bacillus sp. KUN-17

Abstract

γ-Glutamyl transpeptidase (γ-GTP; EC 2.3.2.2) present in the culture filtrate of Bacillus sp. KUN-17 was purified 400-fold through a consecutive procedure including organic precipitation and column chromatography. The enzyme has an estimated molecular weight of 70,000 and consists of hetero-subunits with molecular weights of 42,000 and 22,000. In vitro optimal conditions for those transfer and hydrolysis reactions appeared to be pH 7.0 at 50°C and pH 8.4 at 40°C, respectively. The denatured enzyme recovered most of its γ-GTP activity by removing detergents such as sodium dodecyl sulfate (SDS) or urea with dialysis. The enzyme showed higher affinities against a number of amino acids as γ-glutamyl acceptors than glycylglycine in the following order: L-valine, L-methionine, L-glutamic acid or L-asparagine, L-alanine. Also, it was shown that L-glutamine was the most suitable γ-glutamyl donor for the transfer reaction among those tested. Amino acids generally inhibited the enzyme activity for the transfer reaction, but not for the hydrolysis reaction.