Phosphoenolpyruvate carboxylase

phosphoenolpyruvate carboxylase
Identifiers
EC number	4.1.1.31
CAS number	9067-77-0
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
Search PMC articles PubMed articles

Phosphoenolpyruvate carboxylase
Identifiers
Symbol	PEPcase
Pfam	PF00311
InterPro	IPR001449
PROSITE	PDOC00330
SCOP	1fiy
Available protein structures: Pfam structures PDB RCSB PDB; PDBe PDBsum structure summary

Phosphoenolpyruvate carboxylase (also known as PEP carboxylase, PEPCase, or PEPC; EC 4.1.1.31) is an enzyme in the family of carboxy-lyases that catalyzes the addition of bicarbonate to phosphoenolpyruvate (PEP) to form the four-carbon compound oxaloacetate:

PEP + HCO₃^- → oxaloacetate + Pi

This reaction is used for carbon fixation in so-called "CAM" and "C4" plants where it plays a key role in photosynthesis. The enzyme is also found in some bacteria, but not in animals or fungi.^[1]

PEP carboxylase in photosynthesis

After conversion of CO₂ to bicarbonate by carbonic anhydrase, PEP carboxylase assimilates the available bicarbonate into a four-carbon compound (oxaloacetate, which is further converted to malate) that can be stored or shuttled between plant cells. This allows for a separation of initial carbon fixation by contact with air and secondary carbon fixation into sugars by RuBisCO during the light-independent reactions of photosynthesis.

In succulent CAM plants adapted for growth in very dry conditions, PEP carboxylase fixes bicarbonate during the night when the plant opens its stomata to allow for gas exchange. During the day time, the plant closes the stomata to preserve water and releases CO₂ inside the leaf from the storage compounds produced during the night. This allows the plants to thrive in dry climates by conducting photosynthesis without losing water through open stomata during the day.

In C4 plants, for example maize, PEP carboxylase fixes bicarbonate in the mesophyll cells of the leaf and the resulting four-carbon compound, malate, is shuttled into the bundle sheath cells where it releases CO₂ for fixation by RuBisCO. Thus, the two processes are separated spatially, allowing for RuBisCO to operate in a low-oxygen environment to circumvent photorespiration. Photorespiration occurs due to the inherent oxygenase activity of RuBisCO in which the enzyme uses oxygen instead of carbon dioxide without incorporating carbon into sugars or generating ATP. As such, it is a wasteful reaction for the plant. By comparison, C4 carbon fixation via PEP carboxylase is more efficient.

Notes

1. ^ NCBI BLINK entry for Arabidopsis PEP carboxylase

External links

• MeSH Phosphoenolpyruvate+Carboxylase
• Overview at wustl.edu
• Diagram of mechanism at gla.ac.uk
• Diagram of reaction at plantphys.net

This enzyme-related article is a stub. You can help Wikipedia by expanding it.v · Categories: Enzymes Photosynthesis Enzyme stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем решить контрольную работу Cathedral of St. John the Baptist, Przemyśl Wildflower! Arts and Music Festival Look at other dictionaries: Phosphoénolpyruvate carboxylase — ] PEPC d’E. coli. PDB 1FIY …   Wikipédia en Français Phosphoenolpyruvate carboxykinase — Not to be confused with Phosphoenolpyruvate carboxylase. Phosphoenolpyruvate carboxykinase PDB rendering based on 1khb. Identifiers Symbol …   Wikipedia Phosphoenolpyruvate — Chembox new ImageFile=Phosphoenolpyruvic acid.svg ImageSize= IUPACName=2 phosphonooxyprop 2 enoic acid OtherNames=Phosphoenolpyruvic acid, PEP Section1= Chembox Identifiers CASNo=138 08 9 PubChem=1005 ChemSpiderID = 980… …   Wikipedia Pyruvate carboxylase — Protein Name=PAGENAME caption= Symbol=PC AltSymbols= HGNCid=8636 Chromosome=11 Arm=q Band=11 LocusSupplementaryData= q13.1 ECnumber=6.4.1.1 OMIM=608786 EntrezGene=5091 RefSeq=NM 000920 UniProt=P11498 PDB=Pyruvate carboxylase is an enzyme of the… …   Wikipedia PEP carboxylase — Enzyme responsible for the primary fixation of CO2 in C4 plants. Carboxylates PEP (phosphoenolpyruvate) to give oxaloacetate. Also important in crassulacean acid metabolism, since it is responsible for CO2 fixation in the dark …   Dictionary of molecular biology RubisCO — Ribulose 1,5 diphosphate carboxylase/oxygénase (RuBisCO)   N° EC   EC …   Wikipédia en Français PHOTOSYNTHÈSE — Le terme «photosynthèse» signifie littéralement: synthèse réalisée à l’aide de l’énergie lumineuse. Bien que, en ce sens, différentes réactions synthétiques puissent avoir lieu indépendamment des êtres vivants, il est d’usage de ne désigner par… …   Encyclopédie Universelle List of EC numbers (EC 4) — This list contains a list of EC numbers for the fourth group, EC 4, lyases, placed in numerical order as determined by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology.EC 4.1: Carbon Carbon LyasesEC… …   Wikipedia Carboxy-lyases — Carboxy lyases, also known as decarboxylases, are carbon–carbon lyases that add or remove a carboxyl group from organic compounds. These enzymes catalyze the decarboxylation of amino acids, beta keto acids and alpha keto acids[1]. Contents 1… …   Wikipedia Malonyl-CoA decarboxylase — Identifiers EC number 4.1.1.9 CAS number 9024 99 1 …   Wikipedia 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”