Regulation of alpha-ketoglutarate dehydrogenase cooperative properties in substrate binding by thiol-disulfide exchange.

The influence of reducing the KGD non-cooperative form by DTT on the KG binding by the enzyme was investigated. The chemical modification of KGD by DEP has revealed that reduction of KGD cysteine residues results in the appearance of the interaction of the dimer active sites upon the enzyme-substrate complex formation. The reduction of 2 SH-groups per KGD subunit: the most reactive one and a buried one--was established to be sufficient for the appearance of KGD cooperative properties in substrate binding as well as for the change in the enzyme activity plots versus substrate concentration. It is suggested that KGD can be regulated by thiol-disulfide exchange in the cell.