Differential effects of magnesium on the hydrolysis of ADP and ATP in human term placenta. Effect of substrates and potassium.
This study evaluates the effect of Mg2+ on the extramitochondrial hydrolysis of ATP and ADP by human term placental mitochondria (HPM) and submitochondrial particle (SMP). Extramitochondrial ATPase and ADPase activities were evaluated in the presence or absence of K+, and different oxidizable substrates. Mg2+ increased both ATP and ADP hydrolysis according to the experimental conditions, and this stimulation was related to the mitochondrial intactness. The ADPase activity in intact mitochondria is 100-fold higher in presence of K+, succinate and 1mM Mg2+ while this activity is only increased by two-fold on the SMP when compared to the sample without Mg2+. It is clearly demonstrated that up-regulation of these enzyme activities occur in intact mitochondria and not on the enzyme itself. The results suggest that the regulation of ATP and ADP hydrolysis is complex, and Mg2+ plays an important role in the modulation of the extramitochondrial ATPase and ADPase activities in HPM
Martínez
Federico
F
Departamento de Bioquímica, Facultad de Medicina, UNAM Apdo, Postal 70-159, Mexico City, Mexico. fedem@servidor.unam.mx
Uribe
Aida
A
Milán
Rebeca
R
Teresa Espinosa-García
M
M
Gracía-Pérez
Cecilia
C
Flores-Herrera
Oscar
O
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D005260:Female; D006801:Humans; D006868:Hydrolysis; D007523:Isocitrates / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*; D008293:Malates / Q000378:metabolism; D010920:Placenta / Q000378:metabolism*; D011189:Potassium Chloride / Q000378:metabolism* / Q000494:pharmacology; D011247:Pregnancy; D013379:Substrate Specificity; D019802:Succinic Acid / Q000378:metabolism
D007523:Isocitrates; D007656:Ketoglutaric Acids; D008293:Malates; D000244:Adenosine Diphosphate; D011189:Potassium Chloride; C030298:malic acid; D000255:Adenosine Triphosphate; C034219:isocitric acid; D019802:Succinic Acid; D008274:Magnesium