Development of C4 photosynthesis in sugar cane: Changes in properties of phosphoenolpyruvate carboxylase during greening

Abstract

Phosphoenolpyruvate (PEP) carboxylase extracted from etiolated and greening sugar cane (a Saccharum hybrid) displayed different properties in terms of DEAE-cellulose elution profile and activation by glucose-6-phosphate. During the first 20 hours of greening, no increase in extractable PEP carboxylase activity was observed, but ionic and allosteric properties of the enzyme changed, becoming similar to those found for the enzyme from light-grown cane. Density labelling studies with deuterium oxide provided no evidence for either de novo synthesis or turnover of the enzyme during this period, or during the following 24 hours of greening. These results are discussed in relation to enzyme control mechanisms and the development of the C₄ pathway in photosynthesis.