THE STRUCTURE AND FUNCTION OF PQQ-CONTAINING QUINOPROTEINS [Review]

摘要

About 30 years ago, it was shown that bacterial methanol and glucose dehydrogenases contained a completely novel type of prosthetic group which was subsequently identified as pyrrolo-quinoline quinone (PQQ). Quinoproteins were originally 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 and related proteins. The basic structure is a 'propeller' fold superbarrel structure made up of 8 beta-sheet 'propeller blades) which are held together by novel tryptophan-docking motifs. 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 these in relation to previously proposed mechanisms for this enzyme. [References: 71]