Translational control of alpha-amylase gene expression in Aspergillus awamori

Regulation of alpha-amylase gene expression in Aspergillus awamori was studied by analyzing the enzyme activity levels, rate of protein synthesis, and alpha-amylase-specific mRNA levels under various conditions of growth. alpha-Amylase synthesis was sensitive to catabolite repression as glucose repressed its synthesis by about fourfold. The stimulation of alpha-amylase synthesis in the presence of its substrate starch was shown to be due to derepression rather than induction as the enzyme was synthesized at similar rates in both starch and starvation media. Repression and derepression of enzyme synthesis was found to be mediated at the translational level. The cellular levels of alpha-amylase-specific mRNA as measured by an in vitro translation assay system, were almost identical under all conditions of enzyme synthesis. Relative in vivo and in vitro alpha-amylase mRNA template activities suggest that alpha-amylase mRNA is translated much more efficiently during the derepression than under the conditions of repressed synthesis.