Purification and properties of aromatic amino acid aminotransferases from Azospirillum brasilense UAP 14 strain
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L Soto-Urzua1, Y G Xochinua-Corona, M Flores-Encarnacion
1Centro de Investigaciones Microbiológicas, Universidad Autónoma, de Puebla, México.
Abstract:
The purification and characterization of AAT1, one of two aromatic amino acid aminotransferase (EC 2.6.1.57) in Azospirillum brasilense, is described. Purified AAT1 had a subunit mass of 33 kDa and a nondenatured molecular mass of 66 kDa, suggesting a dimeric structure. Other properties include a pI of 5.04, an optimum temperature of 45 degrees C, and optimum pH of 8.5. AAT1 utilized all aromatic amino acids, the L-tryptophan derivatives such as L-5-methyl tryptophan and L-flour-tryptophan, and L-histidine. The apparent Km values for L-tyrosine, L-phenylalanine, and L-tryptophan were 0.19, 0.43, and 1.05 mM, respectively. The enzyme was competive inhibited by indole-3-pyruvic acid with a Ki of 0.17 mM.