Na,K-pump reaction kinetics at the tip of a patch electrode: derivation of reaction kinetics for electrogenic and electrically silent reactions during ion transport by the Na,K-ATPase.

Patch-clamp electrophysiological techniques allow manipulations of electrochemical driving forces for ion transport by the Na,K-ATPase. For this reason, this technique has been used to study steady-state ion transport properties of the Na,K-ATPase. High temporal resolution during these manipulations also permits rapid reactions, such as extracellular ion-binding reactions, to be measured as charge movements when the enzyme is engaged in electroneutral ion exchange modes. Just as useful, but less widely recognized, is the ease with which electrophysiological techniques can be used to critically study reaction steps that do not directly involve ion binding. Three studies are briefly presented to show how pre-steady-state and/or steady-state electrophysiological techniques can be used to study ion-binding reactions in a novel fashion and the kinetics of electrically silent reaction steps of this enzyme. The reaction kinetics derived from each of these studies can be used to attain detailed mechanistic information about ion transport by the Na,K-ATPase.