Dataset Information

Glutamine 89 is a key residue in the allosteric modulation of human serine racemase activity by ATP.

ABSTRACT: Serine racemase (SR) catalyses two reactions: the reversible racemisation of L-serine and the irreversible dehydration of L- and D-serine to pyruvate and ammonia. SRs are evolutionarily related to serine dehydratases (SDH) and degradative threonine deaminases (TdcB). Most SRs and TdcBs - but not SDHs - are regulated by nucleotides. SR binds ATP cooperatively and the nucleotide allosterically stimulates the serine dehydratase activity of the enzyme. A H-bond network comprising five residues (T52, N86, Q89, E283 and N316) and water molecules connects the active site with the ATP-binding site. Conservation analysis points to Q89 as a key residue for the allosteric communication, since its mutation to either Met or Ala is linked to the loss of control of activity by nucleotides. We verified this hypothesis by introducing the Q89M and Q89A point mutations in the human SR sequence. The allosteric communication between the active site and the allosteric site in both mutants is almost completely abolished. Indeed, the stimulation of the dehydratase activity by ATP is severely diminished and the binding of the nucleotide is no more cooperative. Ancestral state reconstruction suggests that the allosteric control by nucleotides established early in SR evolution and has been maintained in most eukaryotic lineages.

SUBMITTER: Canosa AV

PROVIDER: S-EPMC5998037 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Glutamine 89 is a key residue in the allosteric modulation of human serine racemase activity by ATP.

Canosa Andrea V AV Faggiano Serena S Marchetti Marialaura M Armao Stefano S Bettati Stefano S Bruno Stefano S Percudani Riccardo R Campanini Barbara B Mozzarelli Andrea A

Scientific reports 20180613 1

Serine racemase (SR) catalyses two reactions: the reversible racemisation of L-serine and the irreversible dehydration of L- and D-serine to pyruvate and ammonia. SRs are evolutionarily related to serine dehydratases (SDH) and degradative threonine deaminases (TdcB). Most SRs and TdcBs - but not SDHs - are regulated by nucleotides. SR binds ATP cooperatively and the nucleotide allosterically stimulates the serine dehydratase activity of the enzyme. A H-bond network comprising five residues (T52, ...[more]

PMID: 29899358

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Project description:Residue 225 in serine proteases is typically Pro or Tyr and specifies an important and unanticipated functional aspect of this class of enzymes. Proteases with Y225, like thrombin, are involved in highly specialized functions like blood coagulation and complement that are exclusively found in vertebrates. In these proteases, the catalytic activity is enhanced allosterically by Na+ binding. Proteases with P225, like trypsin, are typically involved in digestive functions and are also found in organisms as primitive as eubacteria. These proteases have no requirement for Na+ or other monovalent cations. The molecular origin of this physiologically important difference is remarkably simple and is revealed by a comparison of the Na+ binding loop of thrombin with the homologous region of trypsin. The carbonyl O atom of residue 224 makes a key contribution to the coordination shell of the bound Na+ in thrombin, but is oriented in a manner incompatible with Na+ binding in trypsin because of constraints imposed by P225 on the protein backbone. Pro at position 225 is therefore incompatible with Na+ binding and is a direct predictor of the lack of allosteric regulation in serine proteases. To directly test this hypothesis, we have engineered the thrombin mutant Y225P. This mutant has lost the ability to bind Na+ and behaves like the allosteric slow (Na(+)-free) form. The Na(+)-induced allosteric regulation also bears on the molecular evolution of serine proteases. A strong correlation exists between residue 225 and the codon used for the active site S195. Proteases with P225 typically use a TCN codon for S195, whereas proteases with Y225 use an AGY codon. It is proposed that serine proteases evolved from two main lineages: (i) TCN/P225 with a trypsin-like ancestor and (ii) AGY/Y225 with a thrombin-like ancestor. We predict that the Na(+)-induced allosteric regulation of catalytic activity can be introduced in the TCN/P225 lineage using the P225Y replacement.

Dataset Information

Glutamine 89 is a key residue in the allosteric modulation of human serine racemase activity by ATP.

Publications

Glutamine 89 is a key residue in the allosteric modulation of human serine racemase activity by ATP.

Similar Datasets

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