THE EFFECT OF MN2-MUSCLE 2-OXOGLUTARATE DEHYDROGENASE COMPLEX( ON THECATALYTIC FUNCTION OF HEART)

The possibile role of Mn2+ in controlling the catalytic function of bi son heart 2-oxoglutarate dehydrogenase complex (OGDC) was investigated . It was established that Mn2+ considerably decreases the S-0.5 value of purified OGDC for 2-oxoglutarate without any notable change in the maximum reaction rate. The OGDC is sensitive to Mn2+ in a wide range o f concentrations. Manganese ions (maintained at 1-2. mu M by a Mn2+-EG TA buffer) reduces the S-0.5 for 7-oxoglutarate approximately 50-fold (from 25.1 to 0.49 mM). At the unsaturating level of 2-oxoglutarate, t he Mn2+ concentration which maximally activates the OGDC is 2 mM. In t he presence of this concentration of Mn2+, the additive effect of aden osine diphosphate on the S-0.5 value of OGDC for 2-oxoglutarate is obs erved.