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Scientific article
English

A substrate-induced change in the stereospecificity of the serine-hydroxymethyltransferase-catalysed exchange of the alpha-protons of amino acids: evidence for a second catalytic site

Published inEuropean journal of biochemistry, vol. 252, no. 1, p. 113-117
Publication date1998
Abstract

NMR has been used to study the catalysis of the hydrogen-deuterium exchange of the alpha-protons of amino acids by serine hydroxymethyltransferase (EC 2.1.2.1) from Escherichia coli. 13C-NMR was used to follow the exchange of the alpha-protons of [2-13C]glycine. The enzyme-catalysed first-order exchange rate of the pro-2S proton of glycine was approximately 7000 times more efficient than that of the pro-2R proton of glycine at both pH 7.0 and 7.8. 1H-NMR was used to follow the hydrogen-deuterium exchange rates of the alpha-protons of L- and D-2-amino derivatives of butyric, pentanoic and hexanoic acids at pH 7.8. Increasing the size of the R-group leads to a progressive change in the stereospecificity of the exchange reaction from the pro-2S proton of glycine to the 2R proton of L-amino acids. The stereospecificity for the alpha-protons of L-amino acids increased as the size of the R-group increased. With glycine, removal of tetrahydrofolate led to a large decrease in the stereospecificity of the exchange reaction but did not affect the exchange rates of the alpha-protons of any of the larger amino acids studied. We show that the Schiff base formed between L-2-aminohexanoic acid (L-norleucine) and pyridoxal 5'-phosphate binds at a different site from the Schiff base between glycine and pyridoxal 5'-phosphate. The molecular basis of these results is discussed.

Keywords
  • Amino Acids/metabolism
  • Bacterial Proteins/metabolism
  • Binding Sites/physiology
  • Borohydrides/metabolism
  • Butyrates/metabolism
  • Caproates/metabolism/pharmacology
  • Carbon Isotopes
  • Catalysis
  • Deuterium
  • Escherichia coli/enzymology
  • Glycine/metabolism/pharmacology
  • Glycine Hydroxymethyltransferase/metabolism
  • Kinetics
  • Molecular Conformation
  • Pentanoic Acids/metabolism
  • Protons
  • Pyridoxal Phosphate/metabolism
  • Schiff Bases/metabolism
  • Substrate Specificity
  • Tetrahydrofolates/metabolism
Affiliation Not a UNIGE publication
Citation (ISO format)
FITZPATRICK, Thérésa Bridget, MALTHOUSE, J P. A substrate-induced change in the stereospecificity of the serine-hydroxymethyltransferase-catalysed exchange of the alpha-protons of amino acids: evidence for a second catalytic site. In: European journal of biochemistry, 1998, vol. 252, n° 1, p. 113–117.
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Article (Published version)
accessLevelRestricted
Identifiers
ISSN of the journal0014-2956
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