1. l-Arabinose induces d-galactose catabolism via the Leloir pathway in Aspergillus nidulans.
- Author
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Németh Z, Kulcsár L, Flipphi M, Orosz A, Aguilar-Pontes MV, de Vries RP, Karaffa L, and Fekete E
- Subjects
- Aspergillus nidulans metabolism, Galactans genetics, Galactans metabolism, Gene Expression Regulation, Fungal, Metabolic Networks and Pathways genetics, Metabolism genetics, Pectins genetics, Pectins metabolism, Polysaccharides genetics, Polysaccharides metabolism, UDPglucose 4-Epimerase genetics, UDPglucose 4-Epimerase metabolism, Xylose genetics, Arabinose metabolism, Aspergillus nidulans genetics, Galactose metabolism, Xylose metabolism
- Abstract
l-Arabinose and d-galactose are the principal constituents of l-arabinogalactan, and also co-occur in other hemicelluloses and pectins. In this work we hypothesized that similar to the induction of relevant glycoside hydrolases by monomers liberated from these plant heteropolymers, their respective catabolisms in saprophytic and phytopathogenic fungi may respond to the presence of the other sugar to promote synergistic use of the complex growth substrate. We showed that these two sugars are indeed consumed simultaneously by Aspergillus nidulans, while l-arabinose is utilised faster in the presence than in the absence of d-galactose. Furthermore, the first two genes of the Leloir pathway for d-galactose catabolism - encoding d-galactose 1-epimerase and galactokinase - are induced more rapidly by l-arabinose than by d-galactose eventhough deletion mutants thereof grow as well as a wild type strain on the pentose. d-Galactose 1-epimerase is hyperinduced by l-arabinose, d-xylose and l-arabitol but not by xylitol. The results suggest that in A. nidulans, l-arabinose and d-xylose - both requiring NADPH for their catabolisation - actively promote the enzyme infrastructure necessary to convert β-d-galactopyranose via the Leloir pathway with its α-anomer specific enzymes, into β-d-glucose-6-phosphate (the starting substrate of the oxidative part of the pentose phosphate pathway) even in the absence of d-galactose., (Copyright © 2018 Elsevier Inc. All rights reserved.)
- Published
- 2019
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