title: Interaction of glutathione analogues with Hydra attenuata gamma-glutamyltransferase.
abstract: gamma-Glutamyltransferase activity was studied in extracts of the cnidarian Hydra attenuata. The binding of gamma-glutamyl peptide analogues 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 analogues, 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 degrees C. GSH (reduced glutathione), gamma-Glu-Abu-Gly and gamma-Glu-Met on the other hand did prevent heat denaturation. GSH and analogues of GSH were competitive inhibitors of p-nitroaniline release, but those analogues in which glycine was replaced by 2-aminoisobutyrate, phenylalanine, leucine or tyrosine had Ki values that were approximately five times those of analogues with the cysteine residue replaced.
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D004151:Dipeptides / Q000494:pharmacology; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology; D006358:Hot Temperature; D006829:Hydra / Q000201:enzymology*; D066298:In Vitro Techniques; D007700:Kinetics; D005723:gamma-Glutamyltransferase / Q000037:antagonists & inhibitors*
chemical_list: D000596:Amino Acids; D000814:Aniline Compounds; D004151:Dipeptides; D005723:gamma-Glutamyltransferase; D005978:Glutathione