Analysis of Amino Acid Residues Involved in Catalysis of Polyethylene Glycol Dehydrogenase From Sphingopyxis Terrae, Using Three-Dimensional Molecular Modeling-Based Kinetic Characterization of Mutants

Appl Environ Microbiol. 2006 Jun;72(6):4388-96. doi: 10.1128/AEM.02174-05.

Abstract

Polyethylene glycol dehydrogenase (PEGDH) from Sphingopyxis terrae (formerly Sphingomonas terrae) is composed of 535 amino acid residues and one flavin adenine dinucleotide per monomer protein in a homodimeric structure. Its amino acid sequence shows 28.5 to 30.5% identity with glucose oxidases from Aspergillus niger and Penicillium amagasakiense. The ADP-binding site and the signature 1 and 2 consensus sequences of glucose-methanol-choline oxidoreductases are present in PEGDH. Based on three-dimensional molecular modeling and kinetic characterization of wild-type PEGDH and mutant PEGDHs constructed by site-directed mutagenesis, residues potentially involved in catalysis and substrate binding were found in the vicinity of the flavin ring. The catalytically important active sites were assigned to His-467 and Asn-511. One disulfide bridge between Cys-379 and Cys-382 existed in PEGDH and seemed to play roles in both substrate binding and electron mediation. The Cys-297 mutant showed decreased activity, suggesting the residue's importance in both substrate binding and electron mediation, as well as Cys-379 and Cys-382. PEGDH also contains a motif of a ubiquinone-binding site, and coenzyme Q10 was utilized as an electron acceptor. Thus, we propose several important amino acid residues involved in the electron transfer pathway from the substrate to ubiquinone.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alcohol Oxidoreductases / chemistry*
  • Alcohol Oxidoreductases / genetics
  • Alcohol Oxidoreductases / metabolism*
  • Alphaproteobacteria / enzymology*
  • Alphaproteobacteria / genetics
  • Amino Acid Sequence
  • Amino Acids / analysis
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Base Sequence
  • Catalysis
  • Kinetics
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Oxidoreductases / chemistry*
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism*
  • Plasmids
  • Protein Conformation
  • Protein Structure, Secondary

Substances

  • Amino Acids
  • Bacterial Proteins
  • Oxidoreductases
  • Alcohol Oxidoreductases
  • polyethylene glycol dehydrogenase