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KMID : 0613820180280030351
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Journal of Life Science
2018 Volume.28 No. 3 p.351 ~ p.356
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Kinetic Characterization of an Iron-sulfur Containing Enzyme, L-serine Dehydratase from Mycobacterium tuberculosis H37Rv
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Han Yu-Jeong
Lee Ki-Seog
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Abstract
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L-Serine dehydratase (LSD) is an iron-sulfur containing enzyme that catalyzes the conversion of L-serine to pyruvate and ammonia. Among the bacterial amino acid dehydratases, it appears that only the L-serine specific enzymes utilize an iron-sulfur cluster at their catalytic site. Moreover, bacterial LSDs are classified into four types based on structural characteristics and domain arrangement. To date, only the LSD enzymes from a few bacterial strains have been studied, but more detailed investigations are required to understand the catalytic mechanism of various bacterial LSDs. In this study, LSD type II from Mycobacterium tuberculosis (MtLSD) H37Rv was expressed and purified to elucidate the biochemical and catalytic properties using the enzyme kinetic method. The L-serine saturation curve of MtLSD exhibited a typically sigmoid character, indicating an allosteric cooperativity. The values of Km and kcat were estimated to be 59.35±1.23 mM and 18.12±0.20 s-1, respectively. Moreover, the plot of initial velocity versus D-serine concentration at fixed L-serine concentrations showed a non-linear hyperbola decay shape and exhibited a competitive inhibition for D-serine with an apparent Ki value of 30.46±5.93 mM and with no change in the kcat value. These results provide insightful biochemical information regarding the catalytic properties and the substrate specificity of MtLSD.
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KEYWORD
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Allosteric cooperativity, iron-sulfur cluster, L-serine dehydratase (LSD), Mycobacterium tuberculosis H37Rv, substrate specificity
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