Literature summary for 4.2.1.42 extracted from

Yew, W.S.; Fedorov, A.A.; Fedorov, E.V.; Almo, S.C.; Gerlt, J.A.
Evolution of enzymatic activities in the enolase superfamily: L-talarate/galactarate dehydratase from Salmonella typhimurium LT2 (2007), Biochemistry, 46, 9564-9577.

Search for more literature for 4.2.1.42

Cloned(Commentary)

Cloned (Comment)	Organism
expression in Escherichia coli	Salmonella enterica subsp. enterica serovar Typhimurium
expression in Escherichia coli	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

Crystallization (Commentary)

Crystallization (Comment)	Organism
structures of the wild type enzyme complexed with L-lyxarohydroxamate, and of the K197A mutant complexed with L-glucarate. Residue Lys 197 functions as the galactarate-specific base and His 328 functions as the L-talarate-specific base	Salmonella enterica subsp. enterica serovar Typhimurium
three different crystal forms are grown by hanging drop vapor diffusion at room temperature: (1) selenomethionine (SeMet)-substituted wild type enzyme, (2) wild-type enzyme complexed with Mg2+ and L-lyxarohydroxamate, and (3) the K197A mutant enzyme complexed with Mg2+ and L-glucarate	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

Protein Variants

Protein Variants	Comment	Organism
H328A	inactive. Mutation totally eliminates both the dehydration and epimerization activities using both L-talarate and galactarate	Salmonella enterica subsp. enterica serovar Typhimurium
H328N	inactive. Mutation totally eliminates both the dehydration and epimerization activities using both L-talarate and galactarate	Salmonella enterica subsp. enterica serovar Typhimurium
K197A	inactive mutant enzyme, the structure of the K197A mutant enzyme complexed with Mg2+ and L-glucarate is determined by molecular replacement using the SeMet-substituted STM3697 structure as the search model	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2
K197A	inactive. Mutation totally eliminates both the dehydration and epimerization activities using both L-talarate and galactarate	Salmonella enterica subsp. enterica serovar Typhimurium

KM Value [mM]

KM Value [mM]	KM Value Maximum [mM]	Substrate	Comment	Organism	Structure
0.33	-	galactarate	pH 8.0, 25°C	Salmonella enterica subsp. enterica serovar Typhimurium
0.33	-	galactarate	pH 8.0, 25°C	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

Metals/Ions

Metals/Ions	Comment	Organism	Structure
Mg2+	required	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2
Mg2+	required. Ligands are residues Asp226, Glu252, and Glu278	Salmonella enterica subsp. enterica serovar Typhimurium

Organism

Organism	UniProt	Comment	Textmining
Salmonella enterica subsp. enterica serovar Typhimurium	Q8ZL58	bifunctional L-talarate/galactarate dehydratase, activites of EC 4.2.1.42 and EC 4.2.1.156	-
Salmonella enterica subsp. enterica serovar Typhimurium ATCC 700720	Q8ZL58	bifunctional L-talarate/galactarate dehydratase, activites of EC 4.2.1.42 and EC 4.2.1.156	-
Salmonella enterica subsp. enterica serovar Typhimurium str. LT2	Q8ZL58	-	-

Purification (Commentary)

Purification (Comment)	Organism
-	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

Substrates and Products (Substrate)

Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.	Reac.
galactarate	galactarate i.e. (2R,3S,4R,5S)-2,3,4,5-tetrahydroxyhexanedioate. The enzyme also catalyzes dehydration of L-talarate. The dehydration of L-talarate is accompanied by competing epimerization to galactarate. Little epimerization to L-talarate is observed in the dehydration of galactarate. On the basis of (1) structures of the wild type enzyme complexed with L-lyxarohydroxamate, an analogue of the enolate intermediate, and of the K197A mutant complexed with L-glucarate, a substrate for exchange of the R-proton, and (2) incorporation of solvent deuterium into galactarate in competition with dehydration, it is concluded that Lys197 functions as the galactarate-specific base and His328 functions as the L-talarate-specific base. The epimerization of L-talarate to galactarate that competes with dehydration can be rationalized by partitioning of the enolate intermediate between dehydration (departure of the 3-OH group catalyzed by the conjugate acid of His328) and epimerization (protonation on C2 by the conjugate acid of Lys197). Only galactarate and L-talarate are completely dehydrated by the enzyme. No other acid sugar results in detectable turnover	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2	5-dehydro-4-deoxy-D-glucarate + H2O	-	?
galactarate	-	Salmonella enterica subsp. enterica serovar Typhimurium	(2R,3S)-2,3-dihydroxy-5-oxohexanedioate + H2O	-	?
galactarate	-	Salmonella enterica subsp. enterica serovar Typhimurium ATCC 700720	(2R,3S)-2,3-dihydroxy-5-oxohexanedioate + H2O	-	?

Synonyms

Synonyms	Comment	Organism
STM3697	-	Salmonella enterica subsp. enterica serovar Typhimurium
STM3697	-	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

Temperature Optimum [°C]

Temperature Optimum [°C]	Temperature Optimum Maximum [°C]	Comment	Organism
25	-	assay at	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

Turnover Number [1/s]

Turnover Number Minimum [1/s]	Turnover Number Maximum [1/s]	Substrate	Comment	Organism	Structure
3.6	-	galactarate	pH 8.0, 25°C	Salmonella enterica subsp. enterica serovar Typhimurium
3.6	-	galactarate	pH 8.0, 25°C	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

pH Optimum

pH Optimum Minimum	pH Optimum Maximum	Comment	Organism
8	-	assay at	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

General Information

General Information	Comment	Organism
physiological function	disruption of gene STM3697 diminishes, but does not eliminate, the ability of the organism to utilize galactarate as carbon source. Disruption eliminates the ability to grow on L-talarate	Salmonella enterica subsp. enterica serovar Typhimurium

kcat/KM [mM/s]

kcat/KM Value [1/mMs^-1]	kcat/KM Value Maximum [1/mMs^-1]	Substrate	Comment	Organism	Structure
0.11	-	galactarate	pH 8.0, 25°C	Salmonella enterica subsp. enterica serovar Typhimurium
11	-	galactarate	pH 8.0, 25°C	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

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Release 2023.1 (January 2023)