The Influence of Salts on the Activity of Particulate Cytochrome Oxidase from Roots of Higher Plants.

Abstract

The activity of cytochrome oxidase from all the spp. studied including soybean, tobacco, oat and spinach was markedly influenced by salt. When anions were held constant as chlorides and the effect of cations compared on an equivalent basis, increased concentration of univalent cation salts stimulated activity until a maximum effect was observed at a concentration of approximately 0.12N. Addition of chloride salts of divalent cations was less stimulatory than salts of univalent cations and maximum increase in activity was observed at 0.05N. When the cation of salts was kept constant as Na+, equivalent concentration of Cl-, NO3, SO4, Br-, I- and citrate stimulated enzyme activity in a similar manner. Phosphate (H2PO4+HPO4) resulted in approximately 20% greater activity than other anion salts whereas HCO3 depressed enzyme activity markedly. The influence of salts on the activity of cytochrome oxidase was not an osmotic manifestation, but an absolute salt requirement for cytochrome oxidase was not demonstrated.