Mannitol and Mannitol Dehydrogenases in Conidia of Aspergillus oryzae

Abstract

A sugar alcohol was isolated from the conidia of Aspergillus oryzae and identified as D-mannitol. Two types of D-mannitol dehydrogenases, nicotinamide adenine dinucleotide phosphate-linked and nicotinamide adenine dinucleotide-linked, were found in the conidia. Substrate specificities, pH optima, Michaelis-Menton constants, and the effects of inhibitors were studied. D-Mannitol was converted to fructose by the dehydro-genases. Synthesis of D-mannitol dehydrogenases was not observed during germination; the content of D-mannitol decreased at an early stage of germination. It was assumed, therefore, that D-mannitol might be used as the source of endogenous respiration and provide energy for the germination.