THE ORGANIZATION AND REGULATION OF PLANT GLYCOLYSIS

This review discusses the organization and regulation of the glycolyti c pathway in plants and compares and contrasts plant and nonplant glyc olysis. Plant glycolysis exists both in the cytosol and plastid, and t he parallel reactions are catalyzed by distinct nuclear-encoded isozym es. Cytosolic glycolysis is a complex network containing alternative e nzymatic reactions. Two alternate cytosolic reactions enhance the path way's ATP yield through the use of pyrophosphate in place of ATP. The cytosolic glycolytic network may provide an essential metabolic flexib ility that facilitates plant development and acclimation to environmen tal stress. The regulation of plant glycolytic flux is assessed, with a focus on the fine control of enzymes involved in the metabolism of f ructosed-6-phosphate and phosphoenolpyruvate. Plant and nonplant glyco lysis are regulated from the ''bottom up'' and ''top down,'' respectiv ely. Research on tissue- and developmental-specific isozymes of plant glycolytic enzymes is summarized. Potential pitfalls associated with s tudies of glycolytic enzymes are considered. Some glycolytic enzymes m ay be multifunctional proteins involved in processes other than carboh ydrate metabolism.