Soluble Peroxidase in Fluid from the Intercellular Spaces of Tobacco Leaves

A high proportion of the soluble peroxidase of tobacco (Nicotiana tabacum L. var. Bottom Special) leaves is found in the fluid obtained by centrifugation of a buffer solution previously infiltrated into the intercellular spaces. Only a very small amount of the cytoplasmic enzyme, glucose 6-phosphate dehydrogenase, is present in this fluid. Specific activity data suggest that an active process is responsible for the transfer of soluble peroxidase to the intercellular space and that the intercellular fluid fraction is not simply composed of material moving out of leaf cells by diffusion. The centrifugation method is a satisfactory means of isolating diluted intercellular fluid for biochemical and physiological investigations.