Influence of Ca2+ oscillatory influx on membrane Ca2+-ATPase activity:: a kinetic model

A kinetic model for the membrane Ca2+-ATPase is considered. The catalytic cycle in the model is extended by enzyme auto-inhibition and by oscillatory calcium influx. It is shown that the conductive enzyme activity can be registered as damped or sustained Ca2+ pulses similar to observed experimentally. It is shown that frequency variations in Ca2+ oscillatory influx induce changes of pulsating enzyme activity. Encoding is observed for the signal frequency into a number of fixed levels of sustained pulses in the enzyme activity. At certain calcium signal frequencies, the calculated Ca2+-ATPase conductivity demonstrates chaotic multi-level pulses, similar to those observed experimentally.