Phosphoenolpyruvate carboxykinase in leaves of certain plants which fix CO 2 by the C 4-dicarboxylic acid cycle of photosynthesis

Abstract

Phosphoenolpyruvate carboxykinase has been found in leaves of Panicum maximum, Panicum texanum, and Sporobolus poiretii at levels sufficient to be involved in photosynthesis. The enzyme preferentially utilizes adenosine nucleotide derivatives. In Panicum maximum the enzyme is concentrated in the bundle sheath cells about four times higher than in the mesophyll cells. From 40 to 50 percent of the enzyme activity in bundle sheath cell extracts of Panicum maximum can be separated into a particulate fraction. The enzyme may function as a decarboxylase in bundle sheath cells of certain C 4-dicarboxylic acid cycle plants which have a low content of malic enzyme.