Interactions between cations in modifying the binding of hexokinases I and II to mitochondria

Interactions between cations in modifying the binding of hexokinases I and II to mitochondria was examined with reference to the intracellular condition. Mitochondria-binding of either of hexokinases I and II, both prepared from mouse ascites ELD cells, was markedly increased by Mg2+ as has been known well. However, even in the absence of Mg2+, marked binding was attained by 100 mM K+ alone especially for hexokinase I, which seemed generally more ready to bind to mitochondria. On the other hand, the effect of Mg2+ to increase the binding was reduced by the addition of K+, and the decreasing effect of K+ was much more marked for hexokinase II than I. These results indicate that, in addition to Mg2+, monovalent cations as represented by K+, also have marked effect on the binding, and the effect is different for each hexokinases I and II, which may be responsible for the difference in the intracellular distribution between these hexokinases.