The intracellular distribution of adenylate kinase in the leaves of spinach, wheat and barley.

Of the total adenylate-kinase activity in 10-d-old barley and wheat leaves, 40-50% is localised in the chloroplasts, while in mature spinach leaves 50-70% of the enzyme is chloroplastic. The extra-chloroplastic adenylate-kinase activity is associated with the mitochondria, very little, if any, is freely soluble in the cytoplasm. The adenylate pool of the cytoplasm could have access to adenylate-kinase activity in the intermitochondrial space because of the free permeation of adenylates across the outer mitochondrial membrane. Thus the adenylate pool of the cytoplasm could be subject to adenylate-kinase equilibrium. The mitochondrial adenylate kinase appeared to the localised exclusively in the intermembrane space.