The adenosine diphosphate–adenosine triphosphate-exchange reaction of cerebral microsomes and its relation to the sodium ion-stimulated adenosine-triphosphatase reaction

Publisher Website
Google Scholar
Abstract
Microsomes from guinea-pig cerebral cortex contain a system capable of exchanging ADP with ATP at rates of about 20 [mu]moles/mg of protein/hr. The ADP-ATP-exchange reaction requires Mg2+ for activity. The reaction is not stimulated by Na+ or K+ and is not inhibited by ouabain, in contrast with the Na+-plus-K+-stimulated adenosine triphosphatase. The pH optimum also differs from that of the adenosine triphosphatase. The ADP-ATP-exchange reaction is stimulated 2- to 3-fold by non-ionic, anionic and cationic detergents, even when these agents are inhibiting the adenosine-triphosphatase reaction. This reaction may represent a component of the Na+-plus-K+-stimulated adenosine-triphosphatase reaction but is more likely to be due to other enzyme systems present in microsomal sub-fractions.