Differences in the responses of brain cytosolic and mitochondrial hexokinases to three essential divalent metal ions.
Rat brain cytosolic and mitochondrial hexokinase activities were undetectable without added divalent cations. Mg2+ activated cytosolic (K0.5 of Mg2+ = 343 +/- 13 microM) and mitochondrial (K0.5 of Mg2+ = 183 +/- 8 microM) hexokinase in a concentration-related manner. The corresponding values for Mn2+ were 702 +/- 99 and 413 +/- 21 microM respectively. Ca2+, however, activated both forms of hexokinase poorly. In the presence of Mg2+, both Mn2+ and Cu2+ were more potent inhibitors of cytosolic hexokinase than mitochondrial hexokinase, whereas the inhibition of Cd2+ and Ca2+ did not show such selectivity. These results demonstrate that brain mitochondrial and cytosolic hexokinases differ significantly in their responses to divalent cations.
Lai
J C
JC
Blass
J P
JP
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D006593:Hexokinase / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000494:pharmacology; D008928:Mitochondria / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains
D008345:Manganese; D003300:Copper; D006593:Hexokinase; D008274:Magnesium; D002118:Calcium