Photo regulation of potassium atpase in vitro by red and far red light in extracts from cucumber cucumis sativus cultivar long green ridge hypocotyls
Thomas, B.; Tull, S.E.
Zeitschrift fuer Pflanzenphysiologie 102(4): 283-292
Particulate material from cucumber hypocotyls was purified by differential centrifugation and agarose gel chromatography. The fraction was heterogeneous in nature and contained both phytochrome and ATPase activity. The latter consisted of at least 2 different components, a non-specific acid phosphatase and a potassium stimulated ATPase (K+-ATPase). The K+-ATPase appeared to be strongly inhibited by Ca+2 and was subject to photoregulation by red and far red light (R and F) in vitro. F caused an increase in Km for ATP and this was reversible by subsequent R. No significant effect on Vmax was caused by the light treatments. Photoregulation of ATPase in vitro occurred only if R was given in vivo prior to extraction. The effect of R in vivo was reversible by F indicating that this also was a phytochrome response. The acid phosphatase activity was not subject to photoregulaton but its presence prevented further characterization of the K+-ATPase and its photoregulation. Phytochrome may indirectly affect K+-ATPase by affecting membrane permeability and substrate availability.