title: Investigating the physiological roles of low-efficiency D-mannonate and D-gluconate dehydratases in the enolase superfamily: pathways for the catabolism of L-gulonate and L-idonate.
abstract: The sequence/function space in the D-mannonate dehydratase subgroup (ManD) of the enolase superfamily was investigated to determine how enzymatic function diverges as sequence identity decreases [Wichelecki, D. J., et al. (2014) Biochemistry 53, 2722-2731]. That study revealed that members of the ManD subgroup vary in substrate specificity and catalytic efficiency: high-efficiency (kcat/KM = 10(3)-10(4) M(-1) s(-1)) for dehydration of D-mannonate, low-efficiency (kcat/KM = 10-10(2) M(-1) s(-1)) for dehydration of D-mannonate and/or D-gluconate, and no activity. Characterization of high-efficiency members revealed that these are ManDs in the D-glucuronate catabolic pathway {analogues of UxuA [Wichelecki, D. J., et al. (2014) Biochemistry 53, 4087-4089]}. However, the genomes of organisms that encode low-efficiency members of the ManDs subgroup encode UxuAs; therefore, these must have divergent physiological functions. In this study, we investigated the physiological functions of three low-efficiency members of the ManD subgroup and identified a novel physiologically relevant pathway for L-gulonate catabolism in Chromohalobacter salexigens DSM3043 as well as cryptic pathways for L-gulonate catabolism in Escherichia coli CFT073 and L-idonate catabolism in Salmonella enterica subsp. enterica serovar Enteritidis str. P125109. However, we could not identify physiological roles for the low-efficiency members of the ManD subgroup, allowing the suggestion that these pathways may be either evolutionary relics or the starting points for new metabolic potential.
authors.affiliation: Departments of Biochemistry and Chemistry and Institute for Genomic Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Wichelecki
authors.forename: Jean Alyxa Ferolin
authors.initials: JA
authors.lastname: Vendiola
authors.forename: Amy M
authors.initials: AM
authors.lastname: Jones
authors.forename: Nawar
authors.initials: N
authors.lastname: Al-Obaidi
authors.forename: Steven C
authors.initials: SC
authors.lastname: Almo
authors.forename: John A
authors.initials: JA
authors.lastname: Gerlt
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D055353:Chromohalobacter / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D055786:Gene Knockout Techniques; D020632:Halomonas / Q000201:enzymology / Q000235:genetics; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D053858:Metabolic Networks and Pathways; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D012477:Salmonella enteritidis / Q000201:enzymology / Q000235:genetics; D013379:Substrate Specificity; D013400:Sugar Acids / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D013400:Sugar Acids; C113317:idonic acid; C015252:gulonic acid; D006836:Hydro-Lyases; C020576:gluconate dehydratase; C021545:mannonate dehydratase