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Penicillium camemberti galacturonate reductase: C-1 oxidation/reduction of uronic acids and substrate inhibition mitigation by aldonic acids

Authors :
Kurt Wagschal
Victor J. Chan
William M. Hart-Cooper
Douglas B. Jordan
Source :
International Journal of Biological Macromolecules. 153:1090-1098
Publication Year :
2020
Publisher :
Elsevier BV, 2020.

Abstract

The enzyme galacturonate oxidoreductase PcGOR from Penicillium camemberti reduces the C-1 carbon of D-glucuronate and C-4 epimer D-galacturonate to their corresponding aldonic acids, important reactions in both pectin catabolism and ascorbate biosynthesis. PcGOR was active on both glucuronic acid and galacturonic acid, with similar substrate specificities (kcat/Km) using the preferred co-substrate NADPH. Substrate acceptance extended to lactone congeners, and D-glucurono-3,6-lactone was converted to L-gulono-1,4-lactone, an immediate precursor of ascorbate. Reaction with glucuronate showed only minor substrate inhibition, and the product L-gulonate and L-gulono-1,4-lactone were both found to be competitive inhibitors with Ki in the low mM range. In contrast, reaction with C-4 epimer galacturonate displayed marked substrate inhibition. Moreover, the product L-galactonate and L-galactono-1,4-lactone were observed to mitigate substrate inhibition by galacturonate, with the lactone having a greater effect than the acid.

Details

ISSN :
01418130
Volume :
153
Database :
OpenAIRE
Journal :
International Journal of Biological Macromolecules
Accession number :
edsair.doi.dedup.....8f46e144906446b9c7d2e4bb931bcc4b
Full Text :
https://doi.org/10.1016/j.ijbiomac.2019.10.239