tailieunhanh - Báo cáo khoa học: Relationships between the ethanol utilization (alc ) pathway and unrelated catabolic pathways in Aspergillus nidulans

The ethanol utilization pathway inAspergillus nidulansis a model system, which has been thoroughly elucidated at the biochemical, genetic and molecular levels. Three main ele-ments 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 activa-tion of AlcRby the physiological inducer, acetaldehyde, produced from growth substrates such as ethanol and L-threonine. . | Eur. J. Biochem. 270 3555-3564 2003 FEBS 2003 doi Relationships between the ethanol utilization alc pathway and unrelated catabolic pathways in Aspergillus nidulans Michel Flipphi Janina Kocialkowska and Beatrice Felenbok Institut de Genetique et Microbiologie CNRS UMR 8621 Université Paris-Sud XI Centre d Orsay Orsay France 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 AlcRby 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. These studies allowed us to predict which type of carbonyl compounds might induce the system. In this study we have determined that catabolism of different amino acids such as L-valine L-isoleucine L-arginine and L-proline produces aldehydes that are either not accumulated or fail to induce the alc system. On the other hand catabolism of D-galacturonic acid and putrescine during which aldehydes are transiently accumulated gives rise to induction of the alc genes. We show that the formation of a direct inducer from carboxylic esters does not depend on alcA-encoded alcohol dehydrogenase I or on AlcR and suggest that a cytochrome P450 might be responsible for the initial formation of a physiological aldehyde inducer. Keywords Aspergillus nidulans activation of transcription alc genes aldehydes carboxylic esters. The saprophytic hyphal fungus Aspergillus nidulans can utilize a wide range of organic compounds as sole sources of carbon and nitrogen. One such alternative nutrient is ethanol. The pathway-specific .