Clustered Genes Encoding 2-Keto-l-Gulonate Reductase and l-Idonate 5-Dehydrogenase in the Novel Fungal d-Glucuronic Acid Pathway

D-Glucuronic acid is a biomass component that occurs in plant cell wall polysaccharides and is catabolized by saprotrophic microorganisms including fungi. A pathway for D-glucuronic acid catabolism in fungal microorganisms is only partly known. In the filamentous fungus , the enzymes that are known...

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Published inFrontiers in microbiology Vol. 8; p. 225
Main Authors Kuivanen, Joosu, Arvas, Mikko, Richard, Peter
Format Journal Article
LanguageEnglish
Published Switzerland Frontiers Media S.A 14.02.2017
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Summary:D-Glucuronic acid is a biomass component that occurs in plant cell wall polysaccharides and is catabolized by saprotrophic microorganisms including fungi. A pathway for D-glucuronic acid catabolism in fungal microorganisms is only partly known. In the filamentous fungus , the enzymes that are known to be part of the pathway are the NADPH requiring D-glucuronic acid reductase forming L-gulonate and the NADH requiring 2-keto-L-gulonate reductase that forms L-idonate. With the aid of RNA sequencing we identified two more enzymes of the pathway. The first is a NADPH requiring 2-keto-L-gulonate reductase that forms L-idonate, GluD. The second is a NAD requiring L-idonate 5-dehydrogenase forming 5-keto-gluconate, GluE. The genes coding for these two enzymes are clustered and share the same bidirectional promoter. The GluD is an enzyme with a strict requirement for NADP /NADPH as cofactors. The k for 2-keto-L-gulonate and L-idonate is 21.4 and 1.1 s , and the K 25.3 and 12.6 mM, respectively, when using the purified protein. In contrast, the GluE has a strict requirement for NAD /NADH. The k for L-idonate and 5-keto-D-gluconate is 5.5 and 7.2 s , and the K 30.9 and 8.4 mM, respectively. These values also refer to the purified protein. The deletion resulted in accumulation of 2-keto-L-gulonate in the liquid cultivation while the deletion resulted in reduced growth and cessation of the D-glucuronic acid catabolism.
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Edited by: Michael Sauer, University of Natural Resources and Life Sciences, Vienna, Austria
Present address: Mikko Arvas, The Finnish Red Cross Blood Service, Helsinki, Finland
This article was submitted to Microbial Physiology and Metabolism, a section of the journal Frontiers in Microbiology
Reviewed by: Sonia Cortassa, National Institutes of Health (NIH), USA; David Mousdale, Beocarta Ltd., UK
ISSN:1664-302X
1664-302X
DOI:10.3389/fmicb.2017.00225