Mutant of Escherichia coli Tolerant to the Lysis Induced by Cephalexin |
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Authors: | Toshio Nikaido Shigeo Tomioka Michio Matsuhashi |
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Affiliation: | Institute of Applied Microbiology, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113 Japan |
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Abstract: | 2,3-Diaminopropionate ammonia-lyase (DAPAL), which catalyzes α,β-elimination of 2,3-diaminopropionate regardless of its stereochemistry, was purified from Salmonella typhimurium. We cloned the Escherichia coli ygeX gene encoding a putative DAPAL and purified the gene product to homogeneity. The protein obtained contained pyridoxal 5′-phosphate and was composed of two identical subunits with a calculated molecular weight of 43,327. It catalyzed the α,β-elimination of both D- and L-2,3-diaminopropionate. The results confirmed that ygeX encoded DAPAL. The enzyme acted on D-serine, but its catalytic efficiency was only 0.5% that with D-2,3-diaminopropionate. The enzymologic properties of E. coli DAPAL resembled those of Salmonella DAPAL, except that L-serine, D- and L-β-Cl-alanine were inert as substrates of the enzyme from E. coli. DAPAL had significant sequence similarity with the catalytic domain of L-threonine dehydratase, which is a member of the fold-type II group of pyridoxal phosphate enzymes, together with D-serine dehydratase and mammalian serine racemase. |
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Keywords: | 2 3-diaminopropionate 2 3-diaminopropionate ammonia-lyase D-serine" target="_blank">D-serine Escherichia coli |
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