Relationships between the ethanol utilization (alc) pathway and unrelated catabolic pathways in Aspergillus nidulans.

The ethanol utilization pathway in Aspergillus nidulans is a model system, which has been thoroughly elucidated at the biochemical, genetic and molecular levels. Three main elements are involved: (a) high level expression of the positively autoregulated activator AlcR; (b) the strong promoters of the structural genes for alcohol dehydrogenase (alcA) and aldehyde dehydrogenase (aldA); and (c) powerful activation of AlcR by the physiological inducer, acetaldehyde, produced from growth substrates such as ethanol and l-threonine. We have previously characterized the chemical features of direct inducers of the alc regulon.

Characteristics of physiological inducers of the ethanol utilization (alc) pathway in Aspergillus nidulans.

The ethanol utilization (alc) pathway in Aspergillus nidulans is one of the strongest expressed gene systems in filamentous fungi. The pathway-specific activator AlcR requires the presence of an inducing compound to activate transcription of genes under its control. We have demonstrated recently that acetaldehyde is the sole physiological inducer of ethanol catabolism.