fosfoenolpyruvaatista

Fosfoenolpyruvato carboxilasa, commonly known as phosphoenolpyruvate carboxylase (PEPC), is a cytosolic enzyme that catalyzes the carboxylation of phosphoenolpyruvate (PEP) with bicarbonate to form oxaloacetate and inorganic phosphate. The physiological direction of the reaction is PEP plus bicarbonate to oxaloacetate, contributing to carbon fixation and anaplerosis in various organisms.

PEPC is widespread in bacteria, plants, and certain algae. It plays a central role in C4 photosynthesis and CAM (crassulacean acid metabolism), where it fixes atmospheric CO2 at the site of initial carboxylation and generates oxaloacetate that is subsequently converted to malate and shuttled to specialized cell types. In non-photosynthetic tissues, PEPC provides carbon skeletons for the TCA cycle, supporting anaplerotic replenishment of oxaloacetate.

Structurally, PEPC is typically a homotetramer composed of around 100–110 kDa subunits and requires Mg2+ as a cofactor. Its activity is governed by allosteric effectors that vary among species; malate generally acts as an inhibitor, while activators such as glucose-6-phosphate can increase activity in some contexts. In plants, regulation also occurs via reversible phosphorylation at an N-terminal serine residue by a dedicated PEPC kinase, which raises Vmax and often decreases sensitivity to malate, enabling rapid response to metabolic cues.

Genetically, plants usually possess multiple PEPC gene family members encoding tissue-specific isoforms, whereas bacteria often carry a single ppc gene. The enzyme’s prominence in CO2 fixation has spurred interest in its potential applications for carbon management and biotechnological production of malate-derived compounds. The standard naming in many languages is fosfoenolpyruvato carboxilasa.