• Microbiology and Biotechnology Letters
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• v.23 no.1
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• pp.24-30
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• 1995

The effects of amino acids in growth media on the biosynthesis of Serratia marcescens biodegradative threonine dehydratase activity were examined. The enzyme activity was decreased by 44 and 34% by 10 mM isoleucine and valine, respectively, whereas it was increased approximately by 20% by 10 mM threonine. Among several metabolites tested, pyruvate increased the enzyme activity by 60% at 5 mM, but decreased the enzyme activity approximately by 20 to 70% above 20 mM. The enzyme activity was increased by 64% by 5 mM glyoxylate, whereas it decreased the enzyme activity approximately by 40 to 70% above 20 mM glyoxylate. The thiamine, monopyrrole derivative, also increased the enzyme activity by 84% at 50 $\mu $g/ml, but did not affected the enzyme activity above 300 $\mu $g/ml. cAMP increased the enzyme activity by 58% at 0.5 mM, but decreased the enzyme activity by 15% at 2 mM. These data suggested that the biosynthesis of Serratia marcescens biodegradative threonine dehydratase is regulated by concentrations of pyruvate, glyoxylate and cAMP.

• Proceedings of the Korean Journal of Food and Nutrition Conference
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• 2001.12a
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• pp.121-121
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• 2001

최소 배지에 여러 아미노산과 대사 산물을 첨가하여 배양시킨 Serratia marcescens ATCC 25419 세포추출물에서여 biodegradative threonine dehydratase (BDTD), biosynthetic threonine dehydratase (BSTD)와 acetolactate syntase (ALS)의 비활성도를 조사하였다. S. marcescens BDTD와 ALS는 낮은 농도 (0.5-2 mM)의 cAMP에 의해 촉진적 조절을 받으며, 비교적 낮은 농도의 isoleucine (1-4 mM)에 의해서는 S. marcescens BSTD의 생합성이 증가되고 높은 농도의 isoleucine (10-30 mM)에서는 감소되고 비교적 낮은 농도의 valine (2-4 mM)에 의해서 S. marcescens ALS의 생합성이 증가되는 것으로 보아 S. marcescens ATCC 25419에서 branched chain 아미노산 생합성 과정의 조절 양상은 Escherichia coli K-12와는 달리, isoleucine의 생합성 과정은 BSTD에 의해 조절되고, valine의 생합성 과정은 ALS에 의해 조절되는 것으로 사료된다.

• BMB Reports
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• v.28 no.2
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• pp.124-128
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• 1995

Biodegradative threonine dehydratase purified from Serratia marcescens ATCC 25419 was inactivated by the arginine specific modification reagent, phenylglyoxal (PGO) and the lysine modification reagent, pyridoxal 5'-phosphate (PLP). The inactivation by PGO was protected by L-threonine and L-serine. The second order rate constant for the inactivation of the enzyme by PGO was calculated to be 136 $M^{-1}min^{-1}$. The reaction order with respect to PGO was 0.83. The inactivation of the enzyme by PGO was reversed upon addition of excess hydroxylamine. The inactivation of the enzyme by PLP was protected by L-threonine, L-serine, and a-aminobutyrate. The second order rate constant for the inactivation of the enzyme by PLP was 157 $M^{-1}min^{-1}$ and the order of reaction with respect to PLP was 1.0. The inactivation of the enzyme by PLP was reversed upon addition of excess acetic anhydride. Other chemical modification reagents such as N-ethylmaleimide, 5,5'-dithiobis (2-nitrobenzoate), iodoacetamide, sodium azide, phenylmethyl sulfonylfluoride and diethylpyrocarbonate had no effect on the enzyme activity. These results suggest that essential arginine and lysine residues may be located at or near the active site.

• BMB Reports
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• v.28 no.2
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• pp.118-123
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• 1995

Biodegradative threonine dehydratase was purified to homogeneity from Serratia marcescens ATCC 25419 by streptomycin sulfate treatment, Sephadex G-200 gel filtration chromatography followed by AMP-Sepharose 4B affinity chromatography. The molecular weight of the purified enzyme was 118,000 by fast protein liquid chromatography using superose 6-HR. The enzyme was determined to be a homotetrameric protein with subunit molecular weights of 30,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was inhibited by ${\alpha}-Keto$ acids and their derivatives such as ${\alpha}-ketobutyrate$, pyruvate, glyoxlyate, and phosphoenol pyruvate, but not by ${\alpha}-aminobutyrate$ and ${\alpha}-hydroxybutyrate$. The inhibition of the enzyme by pyruvate and glyoxylate was observed in the presence of AMP. The inhibitory effect of glyoxylate was decreased at high enzyme concentration, whereas the inhibition by pyruvate was independent of the enzyme concentration. The kinetics of inhibition of the enzyme by pyruvate and glyoxylate revealed a noncompetitive and mixed-type inhibition by the two inhibitors with respect to L-threonine and AMP, respectively.