Gene Ontology annotation through association of InterPro records with GO terms

Annotation inferences using phylogenetic trees

Electronic Gene Ontology annotations created by ARBA machine learning models

Combined Automated Annotation using Multiple IEA Methods

Evolution of enzymatic activities in the enolase superfamily: L-talarate/galactarate dehydratase from Salmonella typhimurium LT2.

The activity was discovered by physical screening of an acid-sugar library, not inferred from pathway context, and both substrates are dehydrated efficiently.

"We discovered the function of STM3697 by screening a library of acid sugars; it catalyzes the efficient dehydration of both l-talarate (kcat = 2.1 s-1, kcat/Km = 9.1 x 10(3) M-1 s-1) and galactarate (kcat = 3.5 s-1, kcat/Km = 1.1 x 10(4) M-1 s-1)"
Disruption of STM3697 abolishes growth on L-talarate and only diminishes growth on galactarate, the asymmetry on which the core versus non-core split in this review rests.

"Insertional disruption of the gene encoding STM3697 abolishes this phenotype; this disruption also diminishes, but does not eliminate, the ability of the organism to utilize galactarate as carbon source."
The two substrates are turned over in one active site using different general bases, with Lys197 specific for galactarate and His328 for L-talarate.

"we conclude that Lys 197 functions as the galactarate-specific base and His 328 functions as the l-talarate-specific base"
Three acidic residues coordinate the catalytic magnesium ion.

"Asp 226, Glu 252, and Glu 278 as ligands for the essential Mg2+ at the ends of the third, fourth, and fifth beta-strands"
A third activity, epimerization of L-talarate to galactarate, competes with dehydration and has no GO term.

"The dehydration of l-talarate is accompanied by competing epimerization to galactarate; little epimerization to l-talarate is observed in the dehydration of galactarate."

PMID:29248502

A continuous assay for l-talarate/galactarate dehydratase using circular dichroism.

Recombinant Salmonella enzyme converts meso-galactarate to 5-KDG with kinetics matching the 2007 coupled assay.

"the rates of StTGD-catalyzed conversion of m-galactarate to 5-KDG were determined by following the change in ellipticity at 323 nm"
The newly measured kinetic parameters agree with the original report.

"These values are in excellent agreement with those published previously"

PMID:19883118

Computation-facilitated assignment of the function in the enolase superfamily: a regiochemically distinct galactarate dehydratase from Oceanobacillus iheyensis.

The two dehydratase activities of TalrD/GalrD proceed through a single shared enolate intermediate in one active site.

"We previously characterized a promiscuous acid sugar dehydratase in the MR subgroup that catalyzes both L-talarate dehydratase (TalrD) and GalrD reactions via a common enolate intermediate"
Polarimetry establishes that the Salmonella enzyme dehydrates meso-galactarate to the L-threo product enantiomer, the same one made by GarD-type enzymes.

"TalrD/GalrD produces a product with a positive rotation (2-keto-L-threo-4,5-dihydroxyadipate; 2 in Scheme I)"

PMID:39835335

An Active-Site Bro̷nsted Acid-Base Catalyst Destabilizes Mandelate Racemase and Related Subgroup Enzymes: Implications for Catalysis.

L-talarate/galactarate dehydratase is one of four mandelate racemase subgroup enzymes whose thermostability was measured as a function of its active-site acid-base catalysts.

"four members of the mandelate racemase (MR)-subgroup of the ENS: MR, d-tartrate dehydratase, l-talarate/galactarate dehydratase, and l-fuconate dehydratase"

file:SALTY/STM3697/STM3697-uniprot.txt

UniProtKB reviewed entry Q8ZL58 (TAGAD_SALTY, L-talarate/galactarate dehydratase, Salmonella typhimurium LT2)

Curated function statement giving both dehydration reactions, and stating that L-talarate and L-altrarate are the same compound, which links the paper's substrate name to the GO:1990594 term label.

"Catalyzes the efficient dehydration of both L-talarate (also called L-altrarate) and galactarate to 5-keto-4-deoxy-D-glucarate"
The enzyme's substrate range is restricted to these two aldarates.

"Is not active on other acid sugars"
Curated cofactor annotation assigns one magnesium ion per subunit.

"Binds 1 Mg(2+) ion per subunit."
Curated disruption phenotype distinguishing complete loss of L-talarate utilization from partial impairment of galactarate utilization.

"Cells lacking this gene lose the ability to grow on L-talarate as carbon source, and are impaired in the ability to utilize galactarate as carbon source."
Both general acid/base mutants lose dehydration of both substrates and epimerization, showing the three activities share one active site.

"H->N,A: Loss of dehydration activity on both L-talarate and galactarate and loss of epimerization activity."
Family assignment to the mandelate racemase/muconate lactonizing enzyme family.

"Belongs to the mandelate racemase/muconate lactonizing enzyme family."
The enzyme is a homooctamer built as a tetramer of dimers.

"Homooctamer; tetramer of dimers."