Differential properties of phosphoenolpyruvate carboxylase from etiolated and green sugar cane.

Phosphoenolpyruvate (PEP) carboxylase has been isolated from etiolated and light-grown sugar cane, and a comparison made of the physical and kinetic characteristics of the enzymes. Differences were found in the DEAE-cellulose elution profiles, in saturation kinetics with PEP as variable substrate and with Mg(2+) as variable cofactor, in sensitivities to NaCl as an inhibitor and glucose-6-phosphate as an activator. The etiolated tissue form consistently showed properties resembling more closely PEP carboxylase from a C3 plant than from a C4 plant, with K m PEP and K0.5 Mg values lower than the green tissue form, and markedly less sensitivity to NaCl and glucose-6-phosphate.