AN EXTREME CREA MUTATION IN ASPERGILLUS-NIDULANS HAS SEVERE EFFECTS ON D-GLUCOSE UTILIZATION

Aspergillus nidulans wild-type and the extreme carbon catabolite derep ressed mutant creA(d)-30 were characterized with respect to enzyme act ivities, metabolite concentrations and polyol pools all related to gly colysis, after growth on D-glucose. In the creA(d)-30 strain the enzym es hexokinase and fructose-6-phosphate reductase showed a two- and thr eefold increase in activity, respectively, whereas phosphofructokinase and pyruvate kinase activity decreased two- and threefold, respective ly, in comparison with the wild-type strain, The most notable changes in metabolite concentrations were that fructose 2,C-bisphosphate and f ructose 1,6-bisphosphate showed a 2.5-fold increase, whereas both pyru vate and citrate decreased in the creA(d)-30, Striking differences wer e found for the polyol concentrations measured for the two strains tes ted, Intracellular glycerol and arabitol concentrations were 10-fold h igher and erythritol fivefold higher in creA(d)-30, whereas intracellu lar trehalose and mannitol were both decreased. The total internal pol yol concentration appears to be constant at similar to 700 mu mol (g d ry wt)(-1). AII polyols were also detected in high amounts in the cult ure filtrate of the creA(d)-30 mutant strain but no extracellular treh alose was found, The overall production of polyols in this strain was therefore much higher than in the wild-type, The high level of polyols produced and the changes in metabolite concentrations in the creA(d)- 30 strain suggest that the differences in enzyme activities result in an altered flow through glycolysis leading to a more rapid formation o f polyols which are subsequently secreted.