INHIBITION OF THE XYLOSE ISOMERASE OFPSEUDOMONAS HYDROPHILABY SULPHYDRYL REAGENTS AND THE EFFECT OF GLUTATHIONE

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Abstract
Xylose isomerase of Pseudomonas hydrophila has been found to be strongly inhibited by substances known to combine with or oxidize sulphydryl groups of proteins. Considerable variation exists in the effectiveness of these inhibitors. Complete enzyme inhibition was observed with 2 × 10−4 M p-chloromercuribenzoate and with p-quinone, with 3.3 × 10−2 M N-ethylmaleimide and with 0.3 if iodoacetate. Glutathione, added after the enzyme and the inhibitors had been in solution, reversed only the inhibition caused by p-chloromercuribenzoate. Xylose isomerase, therefore, depends for its activity upon the integrity of sulphydryl groups.