Modification of a catalytically important residue of indoleglycerol-phosphate synthase from Escherichia coli

FEBS Lett. 1989 Mar 13;245(1-2):219-22. doi: 10.1016/0014-5793(89)80225-x.

Abstract

The active-site residues of indoleglycerol-phosphate synthase from Escherichia coli were tentatively localized by comparing crystallographic data with the amino acid identities among the known indoleglycerol-phosphate synthase sequences. To test the validity of the resulting model of catalysis one of the residues in the presumptive active site, Lys 55, was changed to serine using oligonucleotide-directed mutagenesis. The specificity constant kcat/Km of the mutant is 3 x 10(4)-times lower than that of the wild-type enzyme, due to a 60-fold decrease in kcat and a 450-fold increase in Km. This finding shows that Lys 55 is important for both catalysis and substrate binding.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Carboxy-Lyases / metabolism*
  • Catalysis
  • Escherichia coli / enzymology*
  • Indole-3-Glycerol-Phosphate Synthase / genetics
  • Indole-3-Glycerol-Phosphate Synthase / metabolism*
  • Lysine
  • Mutation
  • Serine
  • Structure-Activity Relationship

Substances

  • Serine
  • Carboxy-Lyases
  • Indole-3-Glycerol-Phosphate Synthase
  • Lysine