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  • Title: [Sulfhydryl groups of L-asparaginase A from Pseudomonas fluorescens AG].
    Author: Sokolov NN, Nikolaev AIa.
    Journal: Biokhimiia; 1976 Apr; 41(4):727-31. PubMed ID: 14736.
    Abstract:
    It has been demonstrated that the activity of asparaginase A from Ps. fluorescens AG is completely inhibited by 10(-4) M p-chloromercurybenzoate and by 70-85% by Zn2+, Ca2+ and Cu2+ (2.10(-2) M). Iodoacetate, iodoacetamide, N-ethylimide of maleic acid and 5,5'-dithiobis-(2-nitrobenzoic acid) do not decrease the enzyme activity. Dithiothreitol and beta-mercaptoethanol reactivate the enzyme. L-asparagine, the substrate of asparaginase, protects the enzyme in a large degree against the inhibitory action of p-chloromercurybenzoate. p-chloromercurybenzoate induces a sharp increase in the asparaginase inactivation rate at acidic (6.5--5.5) and alkaline (7.5-8.5) values of pH. The enzyme modification by p-chloromercurybenzoate does not change the Km value for L-asparagine, but decreases Vmax. Thus it may be assumed, that asparaginase from Ps. fluorescens AG contains sulfhydryl groups essential for the enzyme activity.
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