The biogenesis of β-N-(γ-glutamyl)-4-hydroxymethylphenylhydrazine (agaritine) in Agaricus bisporus

According to the biogenetic scheme of Schutte et al. (An. Quim., 1972, 68, 899), agaritine [AG; beta-N-(gamma-glutamyl)-4-hydroxymethylphenylhydrazine (HMPH)], a constituent of the fruit body of the common mushroom Agaricus bisporus, is generally held to be a shikimate-derived metabolite. A critical evaluation of the methodological basis of this tenet showed it is not supported by the experimental data presented. A major doubt concerns the conditions used for hydrolysis of the hydrazide bond; therefore, two derivatives of HMPH, 2- and 4-nitrobenzaldehyde hydrazones, were synthesized as reference compounds for the assessment of the desglutamyl product. The UV-, IR- and H-1 NMR spectroscopic properties of the two new substances are listed. Using (i) the established shikimate-derived metabolite gamma-glutaminyl-4-hydroxybenzene, which co-occurs with AG, as the positive control, (ii) the shikimate-chorismate pathway inhibitor 'glyphosate' as a tool, and (iii) complementary results from physiological experiments, it was demonstrated that there is no de novo synthesis of the desglutamyl moiety of AG in the fruit body. The likely site of AG synthesis is the vegetative hyphae in contact with the wheat straw compost. A speculative scheme is presented for the assembly of AG, which postulates an exogenous origin of both the aryl and the hydrazide moieties of this, resulting, respectively, from the breakdown of lignin by the fungus and the diazotrophic activity of a bacterial commensal in the substratum. (C) 1998 Elsevier Science Ltd. All rights reserved.