Archaeal Mo-Containing Glyceraldehyde Oxidoreductase Isozymes Exhibit Diverse Substrate Specificities through Unique Subunit Assemblies

PLoS One. 2016 Jan 25;11(1):e0147333. doi: 10.1371/journal.pone.0147333. eCollection 2016.


Archaea use glycolytic pathways distinct from those found in bacteria and eukaryotes, where unique enzymes catalyze each reaction step. In this study, we isolated three isozymes of glyceraldehyde oxidoreductase (GAOR1, GAOR2 and GAOR3) from the thermoacidophilic archaeon Sulfolobus tokodaii. GAOR1-3 belong to the xanthine oxidoreductase superfamily, and are composed of a molybdo-pyranopterin subunit (L), a flavin subunit (M), and an iron-sulfur subunit (S), forming an LMS hetero-trimer unit. We found that GAOR1 is a tetramer of the STK17810/STK17830/STK17820 hetero-trimer, GAOR2 is a dimer of the STK23390/STK05620/STK05610 hetero-trimer, and GAOR3 is the STK24840/STK05620/STK05610 hetero-trimer. GAOR1-3 exhibited diverse substrate specificities for their electron donors and acceptors, due to their different L-subunits, and probably participate in the non-phosphorylative Entner-Doudoroff glycolytic pathway. We determined the crystal structure of GAOR2, as the first three-dimensional structure of an archaeal molybdenum-containing hydroxylase, to obtain structural insights into their substrate specificities and subunit assemblies. The gene arrangement and the crystal structure suggested that the M/S-complex serves as a structural scaffold for the binding of the L-subunit, to construct the three enzymes with different specificities. Collectively, our findings illustrate a novel principle of a prokaryotic multicomponent isozyme system.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Archaeal Proteins / chemistry
  • Archaeal Proteins / isolation & purification
  • Archaeal Proteins / metabolism*
  • Crystallography, X-Ray
  • Flavins / analysis
  • Glycolysis
  • Iron-Sulfur Proteins / chemistry
  • Iron-Sulfur Proteins / isolation & purification
  • Iron-Sulfur Proteins / metabolism
  • Isoenzymes / chemistry
  • Isoenzymes / isolation & purification
  • Isoenzymes / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Molecular Weight
  • Molybdenum / analysis
  • Protein Conformation
  • Protein Multimerization
  • Protein Subunits
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Sugar Alcohol Dehydrogenases / chemistry
  • Sugar Alcohol Dehydrogenases / isolation & purification
  • Sugar Alcohol Dehydrogenases / metabolism*
  • Sulfolobus / enzymology*
  • Xanthine Dehydrogenase / classification


  • Archaeal Proteins
  • Flavins
  • Iron-Sulfur Proteins
  • Isoenzymes
  • Protein Subunits
  • Molybdenum
  • Sugar Alcohol Dehydrogenases
  • glyceraldehyde reductase
  • Xanthine Dehydrogenase

Grants and funding

This work was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (to T.W., No. 24580136).