Parallel measurement of oxoglutarate dehydrogenase activity and matrix free Ca2+ in fura-2-loaded heart mitochondria.
The entrapment of the Ca2+-sensitive fluorescence indicators fura-2 or quin2 in the matrix space of isolated heart mitochondria renders possible the direct monitoring of the matrix free Ca2+ [( Ca2+]m) [(1987) Biochem J. 248, 609-613]. In this paper the correlation between the [Ca2+]m and the in situ activity of oxoglutarate dehydrogenase (OGDH) in fura-2-loaded mitochondria is shown. At the initial value of [Ca2+]m, 64 nM, which corresponded to 0.36 nmol/mg mitochondrial Ca content, the OGDH activity was 12% of the maximal. Half-maximal and maximal activation were attained at 0.8 and 1.6 microM [Ca2+]m, respectively. The results indicate that an increase of the mitochondrial Ca content in the physiological range enhances the OGDH activity by means of elevation of [Ca2+]m.
D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D004533:Egtazic Acid; D016257:Fura-2; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism*; D007658:Ketone Oxidoreductases / Q000378:metabolism*; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology*; D009249:NADP / Q000378:metabolism; D051381:Rats; D012430:Ruthenium Red; D013050:Spectrometry, Fluorescence
D001572:Benzofurans; D012430:Ruthenium Red; D004533:Egtazic Acid; D009249:NADP; D007658:Ketone Oxidoreductases; D007655:Ketoglutarate Dehydrogenase Complex; D002118:Calcium; D016257:Fura-2