Abstract

The kinetic properties of phosphorylase (EC 2.4.1.1) and 6-phosphofructokinase (EC 2.7.1.11) extracted from a crassulacean acid metabolism (CAM) plant, Kalanchoe daigremontiana Hamet et Perrier, and a C4 plant, Atriplex spongiosa F. Muell., were compared. The phosphorylase from the CAM plant was strongly inhibited by P1 (1 mM), phosphoenolpyruvate (PEP) (2 mM) and glucose (4 mM). The C4 phosphorylase was less strongly inhibited by P1, and not at all by PEP or glucose. The C4 6-phosphofructokinase was, at Km levels of substrate, about 100 times more sensitive to inhibition by PEP than the CAM enzyme. These results are discussed as the basis for a biochemical regulation of carbohydrate metabolism in CAM plants at night.

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