Garlic Biochemistry in Mushrooms

The genus of onions (Allium) has a diverse pattern of distinct sulphur compounds, which are responsible for the remarkable aroma profiles of garlic (A. sativum L.) and related species. Cysteine sulphoxides of these plants are converted by the enzyme alliinase into the corresponding thiosulphinates, e.g., the thiosulphinate allicin is produced from alliin. Besides onions, also some mushrooms of the class of Basidiomycetes exhibit a strong garlic-like smell and taste. Remarkable are the shiitake mushroom [Lentinus edodes (Berkeley) Pegler] and the garlic parachute Marasmius alliaceus Jacq. Fr.. The cysteine sulphoxide lentinic acid could be already isolated from Lentinus edodes [1]. Similar compounds were assumed for the genus Marasmius. In the actual investigation, Marasmius alliaceus was screened by HPLC-MS/MS for possible atypical cysteine sulphoxides. At least one new sulphur containing compound could be identified. Structure elucidation showed that this substance is a new cysteine sulphoxide with a methylthiomethyl moitey and a second amino acid, glutamate (Figure). In earlier investigations, alliinase of Allium species show no reaction with substrates of Marasmius alliaceus. Consequently, alliinase of Marasmius alliaceus must have unique kinetic properties, which enables the observed rapid cleavage into volatile sulphur compounds. These will be subjects of the ongoing research.

References: [1] Yasumoto, K., Iwani, K. (1987) Meth. Enzymol. 143:434–439.