Comparison of different cations (Mn2+, Mg2+, Ca2+) on the hydrolytic activity of chloroplast ATPase.
The influences of Mn2+, Mg2+, and Ca2+ on the enzymic activity of chloroplast ATPase have been compared, using an HPLC method for the separation of ADP. The dissociation constants of the divalent ion-ATP complexes have been determined by a spectrophotometric method, with the dye antipyrylazo III, and enzymic constants (dissociation constant of the ion-enzyme complexes, Michaelis constants, maximum rates) have been calculated. The comparison between the rates obtained, respectively, with Mn2+ and Ca2+ alone with that given by the mixture of these two ions, allows us to conclude that, as for Mg2+, Mn2+ is also an activator of chloroplast ATPase and that metal-free ATP is the true substrate.
Berger
G
G
Section de Bioénergétique, DBCM, Gif sur Yvette, France.
Girault
G
G
D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D025222:Chloroplast Proton-Translocating ATPases / Q000378:metabolism*; D002736:Chloroplasts / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D006868:Hydrolysis; D007700:Kinetics; D008024:Ligands; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008954:Models, Biological
D008024:Ligands; D008345:Manganese; D000255:Adenosine Triphosphate; D025222:Chloroplast Proton-Translocating ATPases; D008274:Magnesium; D002118:Calcium