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In vitro effect of metal ions on the activity of two amphibian glyceraldehyde-3-phosphate dehydrogenases: potential metal binding sites.

Authors
  • Mounaji, Khadija
  • Vlassi, Metaxia
  • Erraiss, Nour-Eddine
  • Wegnez, Maurice
  • Serrano, Aurelio
  • Soukri, Abdelaziz
Type
Published Article
Journal
Comparative Biochemistry and Physiology Part B Biochemistry and Molecular Biology
Publisher
Elsevier
Publication Date
Jun 01, 2003
Volume
135
Issue
2
Pages
241–254
Identifiers
PMID: 12798935
Source
Medline
License
Unknown

Abstract

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) was purified from two amphibian species, Xenopus laevis and Pleurodeles waltl. Comparative studies revealed that the two proteins differ by their subunit molecular masses, pI values and V8 digested peptide maps. The effect of zinc, cadmium and copper ions on GAPDH enzymatic activity has been examined in vitro. A time, metal concentration and metal type dependent inhibition was observed for both enzymes. X. laevis and P. waltl GAPDHs exhibit a much greater sensitivity to copper than to cadmium or zinc ions. Different half-lives and differential sensitivity to various metals was observed between the two enzymes with P. waltl GAPDH being remarkably tolerant to cadmium ions compared to the X. laevis enzyme. In order to understand the differential sensitivity of the two enzymes to metals, we produced 3D models of both X. laevis and P. waltl GAPDH structures based upon known 3D structures of GAPDHs from other species. This necessitated, in a first step, to clone a 900 bp cDNA fragment encoding the nearly full-length P. waltl GAPDH. Spatial motif searches on the homology models indicated potential metal binding sites involving cysteine and histidine residues outside the catalytic sites, existing only in either the X. laevis or the P. waltl GAPDH sequences.

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