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KMID : 0665220100230020171
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Korean Journal of Food and Nutrition
2010 Volume.23 No. 2 p.171 ~ p.177
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Nucleotide Activation of Catabolic Threonine Dehydratase from Serratia marcescens
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Choi Byung-Bum
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Abstract
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The catabolic threonine dehydratase from Serratia marcescens ATCC 25419 was purified to homogeniety using Sephadex G-200 gel filtration and AMP-Sepharose 4B affinity chromatography. The molecular weight of the native enzyme was 120,000 by native pore gradient PAGE. The enzyme was composed of four identical subunits with subunit molecular weights of 30,000 by SDS-PAGE. The Km values of the enzyme for L-threonine with and without AMP were 7.3 and 92 mM, respectively. There were 2 moles of pyridoxal phosphate and 16 moles of free -SH groups per 1 mole of enzyme. The enzyme was inhibited by -ketobutyrate, pyruvate, glyoxylate, and phosphoenol pyruvate(PEP) in the presence of AMP, yet stimulated by cAMP and ADP. For enzyme properties in comparison with S. marcescens, E. coli, and S. typhimurium enzyme, such as the PLP content, number of free sulfhydryl groups, and existence of ADP binding site, the S. marcescens enzyme was more similar to the S. typhimurium enzyme than the E. coli enzyme. Of the three enteric bacteria, the E. coli and S. typhimurium enzyme was increased the activity by ADP and cAMP, respectively, but only the S. marcescens enzyme was increased the activity by both ADP and cAMP. Therefore, the subtle differences in the properties between enzymes from the three enteric bacteria may represent minor structural differences among these enzymes and warrants further study.
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KEYWORD
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Serratia marcescens, catabolic threonine dehydratase, cAMP, ADP
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