著者

Ueno Yoshie Hayakawa Kiyoshi Takahashi Saori ODA Kohei

出版者

社団法人日本農芸化学会

雑誌

Bioscience, biotechnology, and biochemistry (ISSN:09168451)

巻号頁・発行日

vol.61, no.7, pp.1168-1171, 1997-07-23

被引用文献数

13 135

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Glutamate decarboxylase (GAD) [EC 4.1.1.15] was purified from a cell-free extract of Lactobacillus brevis IFO 12005 by chromatographies on Sephadex G-100, DEAE-Sepharose CL-6B, and Mono Q. About 9 mg of purified GAD was obtained from 90.2 g of wet cells. The purified preparation showed a single protein band on SDS-PAGE. The molecular weights of purified GAD by SDS-PAGE and gel filtration on Superdex 200 were 60,000 and 120,000, respectively, indicating that GAD from L. brevis exists as a dimer. The N-terminal amino acid sequence of the purified GAD was NH_2-Met-Asn-Lys-Asn-Asp-Gln-Glu-Gln-Thr-. The optimum pH and temperature of GAD were at pH 4.2 and at 30℃. The GAD activity was increased by the addition of sulfate ions in a dose-dependent manner. The order of effect was as follows: ammonium sulfate > sodium sulfate > magnesium sulfate, indicating that the increase of hydrophobic interaction between subunits causes the increase of GAD activity. The purified GAD reacted only with L-glutamic acid as asubstrate and the K_m, k_<cat>, and k_<cat>/K_m values were 9.3 mM, 6.5s^<-1>, and 7×10^2 M^<-1>s^<-1>, respectively.