All articles starting with P

Phosphocholine-specific phospholipase C

Phosphocholine-specific phospholipase C (PC-PLC, EC 3.1.4.3), also called non-specific PLC, hydrolyzes phosphatidylcholine to DAG and phosphocholine; bacterial forms are zinc-dependent and structurally solved, while the mammalian gene remains unidentified.

Phosphocreatine

Phosphocreatine (creatine phosphate, PCr) is a phosphorylated creatine energy reserve discovered in 1927 that regenerates ATP via creatine kinase, shuttles phosphate in muscle, and is used clinically in cardiac care.

Phosphodiester bond

A phosphodiester bond, or phosphodiester linkage, is a covalent linkage in which a phosphate joins two fragments through two ester bonds, forming the sugar-phosphate backbone of DNA and RNA.

Phosphodiesterase

Phosphodiesterases (PDE1–PDE11) are enzymes hydrolyzing cAMP and cGMP; PDE5 inhibitors sildenafil, tadalafil, and vardenafil treat erectile dysfunction and pulmonary arterial hypertension, and PDE inhibitors also treat COPD, psoriasis, and atopic dermatitis.

Phosphodiesterase I

Phosphodiesterase I (EC 3.1.4.1, 5′-exonuclease, CAS 9025-82-5) is an oligonucleotide-hydrolyzing enzyme, not the mammalian PDE1 cyclic nucleotide family; produced from Leptographium procerum (GRN 505) for yeast extract 5′-GMP production.

Phosphodiesterase inhibitor

A phosphodiesterase inhibitor, or PDE inhibitor, is a drug blocking enzymes that break down cAMP and cGMP, ranging from theophylline to PDE5 inhibitors for erectile dysfunction.

Oct 15, 2026

Phosphoenolpyruvate

Phosphoenolpyruvate (PEP) is a three-carbon phosphorylated metabolite whose phosphate bond releases about twice the energy of ATP's, and which serves as the final intermediate of glycolysis and the phosphate donor for bacterial sugar import.

Phosphoenolpyruvate carboxykinase deficiency

Phosphoenolpyruvate carboxykinase deficiency (PEPCK deficiency, PEPCK-C deficiency, PCK1/PCK2) is an ultra-rare autosomal recessive gluconeogenesis disorder causing recurrent fasting hypoglycemia, lactic acidosis, liver failure, and TCA-cycle metabolites in urine.

Phosphoenolpyruvate carboxylase

Phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31), also called PEP carboxylase, is a cytosolic plant and bacterial enzyme that irreversibly carboxylates phosphoenolpyruvate with bicarbonate to oxaloacetate and Pi; the C4/CAM photosynthetic isoform performs the first CO2 fixation step and is regulated by N-terminal serine phosphorylation.

Phosphoenolpyruvate guanylyltransferase CofC

Phosphoenolpyruvate guanylyltransferase, called CofC in archaea and FbiD in bacteria, is a GTP-dependent enzyme that activates phosphoenolpyruvate or 2-phospho-L-lactate for the biosynthesis of coenzyme F420.

Phosphoenolpyruvate synthase regulatory protein

Phosphoenolpyruvate synthase regulatory protein (PSRP, E. coli ppsR, UniProt P0A8A4) is a bifunctional kinase-pyrophosphorylase that inactivates PEPS with ADP/ATP and reactivates it with inorganic phosphate, unlike unrelated PSRP abbreviations in biosolids and ribosomal proteins.

Phosphofurin acidic cluster sorting protein 1/2, C-terminal

Phosphofurin acidic cluster sorting protein 1/2, C-terminal (PACS1/2_C) is a conserved protein region at the end of the PACS-1 and PACS-2 sorting proteins, whose function remains undetermined.

Oct 15, 2026

Phosphogenesis

Phosphogenesis is the formation of authigenic phosphate minerals, chiefly carbonate fluorapatite (francolite), in marine sediments, producing phosphorite, a rock with over 18 percent P2O5, mostly in coastal upwelling zones.

Phosphoglucomutase

Phosphoglucomutase (PGM, EC 5.4.2.2) interconverts glucose 1-phosphate and glucose 6-phosphate via a glucose 1,6-bisphosphate intermediate. Human isoenzymes PGM1, PGM2, PGM3, PGM5; PGM1 deficiency causes GSD XIV/PGM1-CDG, treatable with galactose.

Phosphoglycerate kinase

Phosphoglycerate kinase (PGK, EC 2.7.2.3, PGK1/PGK2) is the conserved two-domain, hinge-bending glycolytic enzyme that makes ATP from 1,3-bisphosphoglycerate and ADP; PGK1 mutations cause X-linked hemolytic anemia and myopathy.

Phosphoglycerate Mutase

Phosphoglycerate mutase (PGM, EC 5.4.2.1) is the glycolysis enzyme converting 3-phosphoglycerate to 2-phosphoglycerate. Two unrelated classes exist: cofactor-dependent dPGM with a phosphohistidine intermediate and cofactor-independent iPGM with phosphoserine.

Phosphoglycerate mutase, GpmB, probable

Phosphoglycerate mutase, GpmB, probable (IPR023086) is a bacterial protein family of probable phosphoglycerate mutases in the histidine phosphatase superfamily, named for enterobacterial gpmB; its mutase activity is undemonstrated in E. coli and absent in B. subtilis, and the name has been misapplied to M. tuberculosis GpgP.

Phosphoglycolate phosphatase

Phosphoglycolate phosphatase (PGP, PGLP, PGPase, EC 3.1.3.18) is a HAD-family phosphatase dephosphorylating 2-phosphoglycolate to glycolate: the entry step of plant photorespiration and a metabolite-repair enzyme in bacteria and mammals.

Oct 15, 2026

Phosphogypsum

Phosphogypsum is the calcium sulfate byproduct of wet-process phosphoric acid production, generated at about 5 tons per ton of acid and stockpiled because it contains radioactive radium.

Phosphoinositide 3-kinase

Phosphoinositide 3-kinase (PI3K, phosphatidylinositol-3-kinase): lipid kinase family phosphorylating the 3'-inositol position; three classes, class I isoforms p110α/β/δ/γ; central to PI3K-AKT-mTOR cancer signaling and target of FDA-approved inhibitors like alpelisib and idelalisib.

Phospholamban

Phospholamban (PLN/PLB), a 52-amino-acid cardiac micropeptide, inhibits the SERCA2a calcium pump; PKA phosphorylation at Ser16 relieves inhibition, and PLN mutations cause dilated cardiomyopathy.

Phospholemman

Phospholemman (PLM, FXYD1, ATP1G1) is a 72-amino acid single-pass membrane protein of the FXYD family, the primary PKA/PKC substrate in heart sarcolemma, which inhibits Na/K-ATPase until adrenergic phosphorylation relieves inhibition.

Phospholipase A1

Phospholipase A1 (PLA1, EC 3.1.1.32) is an enzyme that hydrolyzes the sn-1 ester bond of glycerophospholipids, releasing a fatty acid and a lysophospholipid; unlike PLA2, it typically releases saturated or mono-unsaturated fatty acids.

Phospholipase A2

Phospholipase A2 (PLA2), also sPLA2, cPLA2, iPLA2, Lp-PLA2: enzyme family hydrolyzing the sn-2 ester bond of phospholipids to release fatty acids and lysophospholipids, central to eicosanoid and inflammatory signaling, with six subfamilies and drug inhibitors in trials.

Phospholipase B

Phospholipase B (PLB) is an enzyme that removes both sn-1 and sn-2 fatty acyl chains from phospholipids, yielding fatty acids and glycerophosphocholine; a secreted virulence factor of pathogenic fungi and an industrial oil-degumming catalyst.

Phospholipase C

Phospholipase C (PLC), also called phosphoinositide-specific PLC, is a eukaryotic enzyme family hydrolyzing PIP2 into IP3 and DAG second messengers. Six classical families (β, γ, δ, ε, ζ, η) plus one atypical family; PLCβ is Gαq-regulated, PLCγ tyrosine-kinase regulated, PLCε G protein-integrating.

Phospholipase C accessory protein PlcR

Phospholipase C accessory protein PlcR (PA0843, UniProt P40695) is a Pseudomonas aeruginosa chaperone, encoded in the plcHR operon, that binds PlcH 1:1 and is required for its folding, solubility, and secretion; distinct from the Bacillus PlcR regulator.