• Microbiology and Biotechnology Letters
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• v.27 no.3
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• pp.203-207
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• 1999

V. alginolyticus 138-2, a marine halophilic bacterium, produced an extracellular amylase with a molecular weight of ca. 56,000. The analysis of the digestion products of soluble starch by thin layer chromatography(TLC) revealed that the extracellular amylase of V. alginolyticus 138-2 is a saccharifying-type alpha-amylase. The alpha-amylase activity of the culture supernatant of soluble starch was optimal at pH 6.0 and 45$^{\circ}C$. Ca2+ slightly increased the alpha-amylase activity, whereas Hg2+, An2+, Cu2+, Ni2+, Fe2+, and Mn2+inhibited the enzymatic activity. Alkylating thiol group agent, iodoacetic acid did not affect the alpha-amylase activity, but reduced thiol reagents such as dithiothreitol, cysteine, and beta-mercaptoethanol stimulated theenzymatic activity. On the other hand, even if V. alginolyticus 138-2 is a marine halophilic bacterium, its alpha-amylase activity was significantly inhibited by NaCl.

• BMB Reports
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• v.28 no.1
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• pp.40-45
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• 1995

Acetolactate synthase purified from Serratia marcescens ATCC 25419 was rapidly inactivated by the thiol specific reagent p-chloromercuribenzoate (PCMB), the tryptophan specific reagent N-bromosuccinimide (NBS), and the arginine modifying reagent phenylglyoxal (PGO). Inactivation by PCMB was prevented by both ${\alpha}$-ketobutyrate and pyruvate, and the second order rate constant for the inactivation was $2480\;M^{-1}{\cdot}min^{-1}$. The reaction order with respect to PCMB was 0.94. The inactivation of the enzyme by NBS was also substantially reduced by both ${\alpha}$-ketobutyrate and pyruvate. The second order rate constant for inactivation by NBS was $15,000\;M^{-1}{\cdot}min^{-1}$, and the reaction order was 2.0. On the other hand, inactivation by PGO was partially prevented by ${\alpha}$-ketobutyrate, but not by pyruvate. The second order rate constant for the inactivation was $1480\;M^{-1}{\cdot}min^{-1}$ and the order of reaction with respect to PGO was 0.75. These results suggest that essential cysteine, tryptophan and arginine are located at or near the substrate binding site.