[A theoretical study on the regulation mechanism of Ca2+ concentration in lens related to the Ca2+ dependence of Ca2(+)-ATPase activity].
A four-state model for the elementary process of the Ca2+ active transport system in lens was proposed, and based upon this model the Ca2+ dependence of Ca2(+)-ATPase activity was analyzed. The results indicated that the Ca2(+)-ATPase activity reaches a peak at approximately pCa 4-5, and decreases at higher and lower Ca2+ concentrations. In the range of pCa 5-6, ATPase activity increases with Ca2+ concentration. Therefore, the model accounts for the kinetic properties of Ca2(+)-ATPase is a qualitative way. Moreover, it is proved that the Ca2+ dependence of Ca2(+)-ATPase activity is theoretically based upon the changes in Ca2+ affinity of Ca2+ binding sites and the Ca2+ dependence of Ca2(+)-ATPase activity is possibly involved in the regulation of intracellular Ca2+ concentration in vivo as a switching mechanism.
Imaizumi
M
M
Dept. of Ophthalmol., Medical College of Oita, Japan.
Furushima
M
M
Nakatsuka
K
K
Yamanouchi
U
U
D001693:Biological Transport, Active; D002118:Calcium / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D003198:Computer Simulation; D007908:Lens, Crystalline / Q000201:enzymology / Q000378:metabolism*; D008433:Mathematics; D008962:Models, Theoretical
D000252:Calcium-Transporting ATPases; D002118:Calcium