Characterization of an Aspergillus nidulans L-arabitol dehydrogenase mutant.

The degradation pathway for L-arabinose, which consists of a sequence of alternating reduction and oxidation reactions prior to ultimate phosphorylation, was studied in Aspergillus nidulans wild-type as well as in an L-arabinose non-utilizing mutant. The inability of the mutant to use L-arabinose was caused by the absence of L-arabitol dehydrogenase activity. The effect of the mutation on polyol accumulation patterns was studied upon growth on various carbon sources. The presence of L-arabinose resulted in intracellular accumulation of arabitol in this mutant. Moreover, the mutant secreted arabitol under these conditions and, in contrast to the wild-type, featured enhanced expression of enzymes involved in L-arabinose catabolism as well as of extracellular glycosyl hydrolases involved in degradation of the plant cell wall polysaccharide L-arabinan.