BIOSYNTHESIS OF MANNITOL IN AGARICUS BISPORUS

In cell-free extracts of fruiting bodies of A. bisporus mannitol is shown to be synthesized by a NADPH-dependent reduction of free fructose. In vivo other monoses are also incorporated into the mannitol skeleton, but to a much lesser extent. Formation of this hexitol from glucose proceeds through fructose as an intermediate, whereas mannitol synthesis by a pathway involving reduction of glucose to sorbitol and epimerization of the latter to the polyol in question does not seem to occur, although it was shown that sorbitol exists in the common mushroom. Therefore, fructose would appear to be the obligate precursor of mannitol in this fungus. The experimental results are integrated into the picture of our present knowledge of carbohydrate metabolism in A. bisporus. © 1969 Springer-Verlag.