The structure and function of the PQQ-containing quinoprotein dehydrogenases

Abstract

Bacterial methanol and glucose dehydrogenases containing a novel type of prosthetic group, subsequently identified as pyrrolo-quinoline quinone (PQQ), were first described about 30 years ago. Quinoproteins were originally defined as proteins containing PQQ but this definition has since been broadened to include those proteins containing other types of quinone-containing prosthetic groups, and the X-ray structures of representatives of each type of quinoprotein have recently been published. This review is mainly concerned with the structure and function of the PQQ-containing methanol dehydrogenase, whose structure has been determined at high resolution, and related proteins. Their basic structure consists of a 'propeller' fold superbarrel made up of 8-sheet 'propeller blades' which are held together by novel tryptophan-docking motifs. In methanol dehydrogenase the PQQ in the active site is coordinated to a Ca2+ ion and is maintained in position by a stacked tryptophan and a novel 8-membered ring structure made up of a disulphide bridge between adjacent cysteine residues. This review describes these features and discusses them in relation to previously proposed mechanisms for this enzyme.

Highly Conserved Asp-204 and Gly-776 Are Important for Activity of the Quinoprotein Glucose Dehydrogenase of <i>Escherichia coli</i> and for Mineral Phosphate Solubilization

“…1 and used for 3D structure modeling. As with all quinoproteins [Anthony and Ghosh, 1998], the structure of our model GDH is a super barrel made up of eight topologically identical four-stranded antiparallel ␤ -sheets arranged with radial symmetry like blades of a propeller ( fig. 1 a).…”

Catalytic and Molecular Properties of the Quinohemoprotein Tetrahydrofurfuryl Alcohol Dehydrogenase from Ralstonia eutropha Strain Bo

“…3) was identified as the amino acid located at the bottom of the active site interacting by its phenyl ring with the pyridine ring of PQQ (3,19). The two residues responsible for binding of the Ca 2ϩ ion and the active site base were also conserved in the sequence of TfaA (3,19).…”

Biochemical and structural characterization of quinoprotein aldose sugar dehydrogenase from Thermus thermophilus HJ6: Mutational analysis of Tyr156 in the substrate-binding site

“…PQQ-dependent dehydrogenases are the largest enzyme group within the quinoprotein family [1]. PQQ is synthesized exogenously and then associates with an apoprotein to form the active holoenzyme.…”