An endogenous factor which interacts with synaptosomal membrane Na+, K+ ATPase activation by K+

G. RODRÍGUEZ DE LORES ARNAIZ

NEUROCHEMICAL RESEARCH

SPRINGER/PLENUM PUBLISHERS

Año: 1997 vol. 22 p. 215 - 219

0364-3190

We have already described the separation of two brain soluble fractions by Sephadex G-50, one of which stimulates (peak I) and the other inhibits (peak II) Na+, K+-ATPase and K+-p-nitrophenylphosphatase (K+-p-NPPase) activities. Here we examine the features of synaptosomal membrane p-NPPase activity in the presence and absence of brain peak I. It was observed that stimulation of Mg2+, K+-p-NPPase activity by peak I was concentration dependent, The ability of peak I to stimulate p-NPPase activity was lost by heat treatment followed by brief centrifugation. Pure serum albumin also stimulated enzyme activity. K+-p-NPPase stimulation by peak I proved dependent on K+ concentration but independent of Mg2+ and substrate p-nitrophenylphosphate concentrations. Since our determinations were performed in a non-phosphorylating condition reflecting the Na+, K+-ATPase Na+ site, it is suggested that peak I may stimulate the Na+-dependent enzyme phosphorylation known to take place from the internal cytoplasmic side.