[Quaternary structure and allosteric properties of thiamine pyrophosphokinase from rat liver]

Using electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate thiamine pyrophosphokinase (EC 2.7.6.2) was found to possess quaternary structure and consist of two polypeptide chains. It was shown that besides active centres, the oligomer has allosteric centres for binding of Mg2+ ions, since treatment by HgCl2 and heating of the enzyme lead to complete "desensibilisation". This results in a disappearance of the S-shaped curve of the dependence of reaction rate on Mg2+ concentration, the Hill coefficient coming down to 1. It is assumed that thiamine pyrophosphokinase belongs to the class dissociating regulatory enzymes.