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. 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.
Flipphi
Michel
M
Institut de Génétique et Microbiologie, CNRS UMR 8621, Université Paris-Sud XI, Centre d'Orsay, Orsay, France. filpphi@iata.csic.es
Kocialkowska
Janina
J
Felenbok
Béatrice
B
D000079:Acetaldehyde / Q000378:metabolism / Q000494:pharmacology; D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000444:Aldehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism / Q000494:pharmacology; D001233:Aspergillus nidulans / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004952:Esters / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000431:Ethanol / Q000378:metabolism* / Q000494:pharmacology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal / Q000187:drug effects / Q000502:physiology; D005809:Genes, Regulator / Q000502:physiology; D005838:Genotype; D005990:Glycerol / Q000494:pharmacology; D006603:Hexuronic Acids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology; D007785:Lactose / Q000378:metabolism; D011700:Putrescine / Q000378:metabolism / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
C074202:ALCR protein, Aspergillus nidulans; D000596:Amino Acids; D004268:DNA-Binding Proteins; D004952:Esters; D005656:Fungal Proteins; D006603:Hexuronic Acids; D007783:Lactones; D000431:Ethanol; D005680:gamma-Aminobutyric Acid; D003577:Cytochrome P-450 Enzyme System; D000426:Alcohol Dehydrogenase; D000444:Aldehyde Dehydrogenase; D002265:Carboxylic Ester Hydrolases; D000079:Acetaldehyde; D007785:Lactose; D005990:Glycerol; D011700:Putrescine