Changes in the kinetic properties and phosphorylation state of phospho enolpyruvate carboxylase in Zea maysleaves in reponse to light and dark

In plants such as Zea maysthat carry out C 4metabolism, phospho enolpyruvate carboxylase catalyses the primary fixation of atmospheric CO 2. The properties of this enzyme from Z. maysleaves kept in light and in darkness are different. In brightly illuminated leaves, which are actively fixing CO 2, the enzyme is less sensitive to feedback inhibition by malate and is phosphorylated on one or more serine residues. In darkened leaves, which are not photosynthesising, the enzyme is more sensitive to inhibition by malate and is much less phosphorylated. This indicates that the activity of the enzyme is controlled by a reversible phosphorylation.