Shingo Kakita

YCM1008A, a Novel Ca2+-Signaling Inhibitor, Produced by Fusarium sp. YCM1008

In the course of screening for drugs that suppress the Ca2+-mediated growth inhibition in a yeast mutant, we found that the metabolite of Fusarium sp. strain YCM1008 inhibited Ca2+-signaling. A novel pyrano-pyridone, YCM1008A was isolated from the fermentation broth using HLB column chromatography followed by HPLC, and the structure was elucidated by spectral analysis. YCM1008A suppressed Ca2+-induced growth inhibition of the Saccharomyces cerevisiae (Δzds1Δsyr1) mutant.

A Novel Catalytic Ability of γ-Glutamylcysteine Synthetase of Escherichia coli and Its Application in Theanine Production

γ-Glutamylcysteine synthetase (γGCS, EC 6.3.2.2) catalyzes the formation of γ-glutamylcysteine from L-glutamic acid (Glu) and L-cysteine (Cys) in an ATP-dependent manner. While γGCS can use various amino acids as substrate, little is known about whether it can use non-amino acid compounds in place of Cys. We determined that γGCS from Escherichia coli has the ability to combine Glu and amines to form γ-glutamylamides. The reaction rate depended on the length of the methylene chain of the amines in the following order: n-propylamine > butylamine > ethylamine >> methylamine. The optimal pH for the reaction was narrower and more alkaline than for the reaction with an amino acid. The newly found catalytic ability of γGCS was used in the production of theanine (γ-glutamylethylamine). The resting cells of E. coli expressing γGCS, in which ATP was regenerated through glycolysis, synthesized 12.1 mM theanine (18 h) from 429 mM ethylamine.