BIOACTIVATION OF THE MUSHROOM HYDRAZINE, AGARITINE, TO INTERMEDIATES THAT BIND COVALENTLY TO PROTEINS AND INDUCE MUTATIONS IN THE AMES TEST

The present study was undertaken to establish whether liver and kidney enzyme systems, from rat and mouse, have the potential to metabolise and bioactivate agaritine, ma-L(+)glutamyl)-4-(hydroxymethyl)phenylhyd razine, the most abundant hydrazine present in the edible mushroom Aga ricus bisporus. Agaritine was weakly mutagenic, in the absence of an a ctivation system, in Salmonella typhimurium strain TA104. Rat kidney h omogenates, characterised by high gamma-glutamyl transpeptidase activi ty, enhanced the mutagenic response, In contrast, hepatic microsomes, having very low gamma-glutamyl transpeptidase activity, did not influe nce the mutagenicity of agaritine, However, hepatic microsomes could f urther potentiate the mutagenic response induced by the kidney Agariti ne was a good substrate for purified gamma-glutamyl transpeptidase, be ing converted to a major metabolite, 4-(hydroxymethyl)phenylhydrazine, formed as a result of the loss of the glutamyl moiety, Kidney homogen ates from the rat and mouse also catalysed this reaction, the former b eing the more effective, Metabolism of agaritine was suppressed by ser ine-borate, an inhibitor of gamma-glutamyl transpeptidase, Kidney homo genates from rat and mouse could metabolise agaritine to intermediate( s) that bound covalently to proteins, with the rat preparations being the more effective; covalent binding was inhibited by glutathione, In contrast, hepatic preparations alone were ineffective in producing suc h covalent binding but did further increase the covalent binding media ted by the kidney preparations, It is concluded that rat and mouse kid ney homogenates catalyse the removal of the glutamyl group from agarit ine to yield the reactive free hydrazine, which is further converted t o the highly reactive diazonium ion by hepatic microsomes.