Particulate Adenylic Kinase in Higher Plants.

Abstract

An adenylic kinase has been found associated with lupine and peanut cotyledon mitochondria and also with whole chloroplasts isolated from spinach and tobacco leaves. The mitochondrial enzyme requires treatment with ethylenediamine-tetraacetate to demonstrate a metal requirement. Mg++ is most effective, Mn++, Co++ and Ca++ activate to a lesser extent. The enzyme is unaffected by F" until a concentration of 0.02 [image] is reached at which point the enzyme is inhibited about 40%. There is a 50% loss of activity on heating for 10 minutes at 100[degree] C in 0.1 N HCl. The chloroplast enzyme does not retain the metal as firmly as the mitochondrial adenylic kinase. Mg++ is most effective as an activator. Mn++ and Co++ activate to a lesser degree. Increasing F" concentrations cause increasing inhibition until 0.02 M F~ is reached, at which point the enzyme is approximately 60% inhibited. Increasing F" concentrations above this point does not significantly in-crease the amount of inhibition. The chloroplast enzyme, when solubilized, is unstable to heat-acid treatment. However, when still associated with the chloroplast structure, the enzyme retains a great deal of its activity. The possible role the enzyme fulfills in the process of converting light to chemical energy in photosynthesis, and its function in a broad sense in cell metab-olism is discussed.