Relaxed thiol substrate specificity of glutathione transferase effected by a non-substrate glutathione derivative

• Rat glutathione transferase 4-4 catalysed the conjugation of 2-mercaptoethanol with 1-chloro-2,4-dinitrobenzene in the presence of S-methyl-glutathione. The reaction was linearly dependent on enzyme concentration and saturation was seen with respect to both 2-mercaptoethanol and S-methyl-glutathione concentration. High concentrations of S-methyl-gluta-thione were inhibitory. The results suggest that the natural substrate glutathione has two distinct functions in the normal catalytic reaction, (i) induction of a catalytically competent conformation of the enzyme and (ii) provision of the substrate sulfhydryl group in the reaction catalyzed.

Keyword

Conformational change

Thiol substrate specificity

Reaction mechanism

Glutathione transferase

Glutathione derivative

NATURAL SCIENCES

NATURVETENSKAP

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