Enzyme Activities of the Mannitol Cycle and Some Connected Pathways in Alternaria alternata, with Comments on the Regulation of the Cycle.

Abstract

The specific activities of the following enzymes were measured: mannitol 1-phosphate dehydrogenase, mannitol 1-phosphatase, mannitol dehydrogenase, hexokinase, glucose 6-phosphate dehydrogenase, glucose phosphate isomerase, phosphofructokinase and aldolase. The maximal capacities of the enzymes were calculated and were compared with the metabolic fluxes in the mannitol cycle. No enzyme limitations for the fluxes in the cycle were found. The coenzyme availability may govern the fluxes in the cycle. No large differences in the specific enzyme activities between an alternariol-producing strain and a nonproducing strain were found that could explain the production of the secondary metabolite.