Interaction of glutathione analogues with Hydra attenuata γ-glutamyltransferase

Publisher Website
Google Scholar
Abstract
.gamma.-Glutamyltransferase [EC 2.3.2.2] activity was studied in extracts of the cnidarian H. attenuata. The binding of .gamma.-glutamyl peptide analogs to the enzyme was studied by observing their effects on heat denaturation and their inhibition of p-nitroaniline release from .gamma.-glutamyl p-nitroanilide. Neither position-1 analogs, in which the .gamma.-glutamyl moiety was changed to a .beta.-aspartyl (.beta.-Asp-Abu-Gly) or an .alpha.-glutamyl (Glu-Abu-Gly) linkage, nor glutamate protected the enzyme against inactivation at 58.degree. C. GSH (reduced glutathione), .gamma.-Glu-Abu-Gly and .gamma.-Glu-Met prevented heat denaturation. GSH and analogs of GSH were competitive inhibitors of p-nitroaniline release, but those analogs in which glycine was replaced by 2-aminoisobutyrate, phenylalanine, leucine or tyrosine had Ki values that were about 5 times those of analogs with the cysteine residue replaced.