Phosphoenolpyruvate carboxykinase. I. Its role in gluconeogenesis

Abstract

The de novo synthesis of glucose in mam-malian liver involves a number of enzymatic reactions, some specific to this process and others acting in reverse of their role in gly-colysis (Fig. 1). One of the most important of the characteristically gluconeogenic enzymes is phosphoenolpyruvate carboxykinase (PEP-CK) (EC 4.1.1.32). In this review we will focus on this enzyme, its hormonal regulation and its general role in the regulation of gluco-neogenesis and other pathways, together with our thoughts on potentially important new di-rections of research involving phosphoenol-pyruvate carboxykinase in a variety of species. Properties of the enzyme PEP-CK catalyzes the guanosine triphos-phate (GTP)- or inosine triphosphate (ITP)-dependent carboxylation of oxalacetate via the reaction formula