| 6-phosphofructo-2-kinase |
| Identifiers |
| EC number |
2.7.1.105 |
| CAS number |
78689-77-7 |
| 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 |
| NCBI |
proteins |
|
| fructose-2,6-bisphosphate 2-phosphatase |
| Identifiers |
| EC number |
3.1.3.46 |
| CAS number |
81611-75-8 |
| 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 |
| NCBI |
proteins |
|
| 6-phosphofructo-2-kinase |
|
Structure of PFK2. Shown: kinase domain (cyan) and the phosphatase domain (green).
|
| Identifiers |
| Symbol |
6PF2K |
| Pfam |
PF01591 |
| InterPro |
IPR013079 |
| PROSITE |
PDOC00158 |
| SCOP |
1bif |
| SUPERFAMILY |
1bif |
| Available protein structures: |
| Pfam |
structures |
| PDB |
RCSB PDB; PDBe; PDBj |
| PDBsum |
structure summary |
|
Phosphofructokinase 2 (PFK2) or fructose bisphosphatase 2 (FBPase2), is an enzyme responsible for regulating the rates of glycolysis and gluconeogenesis in the human body. It is a homodimer of 55 kDa subunits arranged in a head-to-head fashion, with each polypeptide chain consisting of independent kinase and phosphatase domain. When Ser-32 of the bifunctional protein is phosphorylated, the negative charge causes the conformation change of the enzyme to favor the FBPase2 activity; otherwise, PFK2 activity is favored.[1] The PFK2 domain is closely related to the superfamily of mononucleotide binding proteins including adenylate cyclase, whereas that of FBPase2 is related to a family of proteins that include phosphoglycerate mutases.
Contents
- 1 Structure
- 2 Function
- 3 Regulation
- 4 Reaction mechanism
- 5 Clinical significance
- 6 Isozymes
- 7 References
- 8 Further reading
- 9 External links
Structure
The monomers of the bifunctional protein are clearly divided into two functional domains. The kinase domain is located on the N-terminal.[2] It consists of a central six-stranded β sheet, with five parallel strands and an antiparallel edge strand, surrounded by seven α helices.[3] The domain contains nucleotide-binding fold (nbf) at the C-terminal end of the first β-strand,[4] and thus resembles the structure of adenylate kinase.
On the other hand, the phosphatase domain is located on the C-terminal.[5] It resembles the family of proteins that include phosphoglycerate mutases (PGMs) and acid phosphatases.[6] The domain has a mixed α/ β structure, with a six-stranded central β sheet, plus an additional α-helical subdomain that covers the presumed active site of the molecule.[3] Finally, N-terminal region modulates PFK2 and FBPase2 activities, and stabilizes the dimer form of the enzyme.[6][7]
Function
When glucose level is low, glucagon is released into the bloodstream, triggering a cAMP signal cascade. In the liver Protein kinase A inactivates the PFK-2 domain of the bifunctional enzyme via phosphorylation, however this does not occur in skeletal muscle. The F-2,6-BPase domain is then activated which lowers fructose 2,6-bisphosphate (F-2,6-BP) levels. Because F-2,6-BP normally stimulates phosphofructokinase-1(PFK1), the decrease in its concentration leads to the inhibition of glycolysis and the stimulation of gluconeogenesis.[8]
On the other hand, when the glucose level increases, the level of fructose 6-phosphate (F6P) subsequently rises and the molecule stimulates phosphoprotein phosphatase-1, which removes phosphoryl group from the bifunctional protein. So PFK2 domain is activated and the kinase catalyzes the formation of F-2,6-BP. Thus, glycolysis is stimulated and gluconeogenesis is inhibited.
Regulation
The allosteric regulation of PFK2 is very similar to the regulation of PFK1.[9] High levels of AMP or phosphate group signifies a low energy state and thus stimulates PFK2. On the other hand, a high concentration of phosphoenolpyruvate(PEP) and citrate signifies that there is a high level of biosynthetic precursor and hence inhibits PFK2. However, unlike PFK1, PFK2 is not affected by the ATP concentration.
Glucagon inhibits PFK2 by activating Protein Kinase A (PKA), which phosphorylates the PFK2 complex and causes its FBPase activity to be favored; via PKA and PFK2/FBP, glucagon decreases [F-2,6-BP], which inhibits glycolysis by allosteric inhibition of PFK1. Insulin activates PFK2 by activating protein phosphatase, which dephosphorylates the PFK-2 complex and causes its PFK2 activity to be favored; via Protein Phosphatase and PFK2, insulin increases [F-2,6-BP], which activates glycolysis by allosteric activation of PFK1, signalling an abundance of glucose
Reaction mechanism
PFK2 is likely to catalyze the "simple" transfer of γ-phosphoryl group of ATP onto the hydroxyl present on C-2 of fructose-6-phosphate. Yet, the formation of fructose 2,6-bisphosphate could theoretically occur by a variety of mechanisms, including the intermediary formation of Fructose-6-phosphate 2-pyrophosphate.[9]
The hydrolysis of fructose 2,6-biphosphate is likely to follow the below steps:[10]
- Histidine acts as a nucleophile and attacks the 2-phosphate of F-2,6-BP
- The stabilization of pentacoordinated transition state by several salt bridges and hydrogen bonding.
- The breakdown of the transition state and the release of F6P.
- Histidine increases the nucleophilicity of water, which attacks phosphohistidine, generating phosphate and newly protonated histidine.
Clinical significance
The Pfkfb2 gene encoding PFK2/FBPase2 protein is linked to the predisposition to schizophrenia.[11] Furthermore, the control of PFK2/FBPase2 activity was found to be linked to heart functioning and the control against hypoxia.[12]
Isozymes
Five mammalian isozymes of the protein have been reported to date, difference rising by either the transcription of different enzymes or alternative splicing.[13][14][15]The isozymes differ radically in their regulation and the discussions above are based on liver isozyme.[3]
Humans genes encoding proteins possessing phosphofructokinase 2 activity include:
- PFKFB1, PFKFB2, PFKFB3, PFKFB4
References
- ^ Kurland IJ, el-Maghrabi MR, Correia JJ, Pilkis SJ (March 1992). "Rat liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. Properties of phospho- and dephospho- forms and of two mutants in which Ser32 has been changed by site-directed mutagenesis". J. Biol. Chem. 267 (7): 4416–23. PMID 1339450.
- ^ Kurland I, Chapman B, Lee YH, Pilkis S (August 1995). "Evolutionary reengineering of the phosphofructokinase active site: ARG-104 does not stabilize the transition state in 6-phosphofructo-2-kinase". Biochem. Biophys. Res. Commun. 213 (2): 663–72. doi:10.1006/bbrc.1995.2183. PMID 7646523.
- ^ a b c Hasemann CA, Istvan ES, Uyeda K, Deisenhofer J (September 1996). "The crystal structure of the bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase reveals distinct domain homologies". Structure. 4 (9): 1017–29. doi:10.1016/S0969-2126(96)00109-8. PMID 8805587.
- ^ Walker JE, Saraste M, Runswick MJ, Gay NJ (1982). "Distantly related sequences in the alpha- and beta-subunits of ATP synthase, myosin, kinases and other ATP-requiring enzymes and a common nucleotide binding fold". EMBO J. 1 (8): 945–51. PMC 553140. PMID 6329717.
- ^ Li L, Lin K, Pilkis J, Correia JJ, Pilkis SJ (October 1992). "Hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. The role of surface loop basic residues in substrate binding to the fructose-2,6-bisphosphatase domain". J. Biol. Chem. 267 (30): 21588–94. PMID 1328239.
- ^ a b Stryer, Lubert; Berg, Jeremy Mark; Tymoczko, John L. (2008). "The Balance Between Glycolysis and Gluconeogenesis in the Liver Is Sensitive to Blood-Glucose Concentration". Biochemistry (Looseleaf). San Francisco: W. H. Freeman. pp. 466–467. ISBN 1-4292-3502-0.
- ^ Tominaga N, Minami Y, Sakakibara R, Uyeda K (July 1993). "Significance of the amino terminus of rat testis fructose-6-phosphate, 2-kinase:fructose-2,6-bisphosphatase". J. Biol. Chem. 268 (21): 15951–7. PMID 8393455.
- ^ Pilkis SJ, Claus TH, Kurland IJ, Lange AJ (1995). "6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase: a metabolic signaling enzyme". Annu. Rev. Biochem. 64: 799–835. doi:10.1146/annurev.bi.64.070195.004055. PMID 7574501.
- ^ a b Van Schaftingen E, Hers HG (August 1981). "Phosphofructokinase 2: the enzyme that forms fructose 2,6-bisphosphate from fructose 6-phosphate and ATP". Biochem. Biophys. Res. Commun. 101 (3): 1078–84. doi:10.1016/0006-291X(81)91859-3. PMID 6458291.
- ^ Lin K, Li L, Correia JJ, Pilkis SJ (April 1992). "Glu327 is part of a catalytic triad in rat liver fructose-2,6-bisphosphatase". J. Biol. Chem. 267 (10): 6556–62. PMID 1313012.
- ^ Stone WS, Faraone SV, Su J, Tarbox SI, Van Eerdewegh P, Tsuang MT (May 2004). "Evidence for linkage between regulatory enzymes in glycolysis and schizophrenia in a multiplex sample". Am. J. Med. Genet. B Neuropsychiatr. Genet. 127B (1): 5–10. doi:10.1002/ajmg.b.20132. PMID 15108172.
- ^ Wang Q, Donthi RV, Wang J, Lange AJ, Watson LJ, Jones SP, Epstein PN (June 2008). "Cardiac phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase increases glycolysis, hypertrophy, and myocyte resistance to hypoxia". Am. J. Physiol. Heart Circ. Physiol. 294 (6): H2889–97. doi:10.1152/ajpheart.91501.2007. PMID 18456722.
- ^ Darville MI, Crepin KM, Hue L, Rousseau GG (September 1989). "5' flanking sequence and structure of a gene encoding rat 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase". Proc. Natl. Acad. Sci. U.S.A. 86 (17): 6543–7. doi:10.1073/pnas.86.17.6543. PMC 297880. PMID 2549541.
- ^ Tsuchiya Y, Uyeda K (May 1994). "Bovine heart fructose 6-P,2-kinase:fructose 2,6-bisphosphatase mRNA and gene structure". Arch. Biochem. Biophys. 310 (2): 467–74. doi:10.1006/abbi.1994.1194. PMID 8179334.
- ^ Sakata J, Abe Y, Uyeda K (August 1991). "Molecular cloning of the DNA and expression and characterization of rat testes fructose-6-phosphate,2-kinase:fructose-2,6-bisphosphatase". J. Biol. Chem. 266 (24): 15764–70. PMID 1651918.
Further reading
- Rider MH, Bertrand L, Vertommen D, Michels PA, Rousseau GG, Hue L (August 2004). "6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase: head-to-head with a bifunctional enzyme that controls glycolysis". Biochem. J. 381 (Pt 3): 561–79. doi:10.1042/BJ20040752. PMC 1133864. PMID 15170386.
External links
- Fructose 2,6-bisphosphatase at the US National Library of Medicine Medical Subject Headings (MeSH)
- 6-phosphofructokinase of Arabidopsis thaliana at genome.jp
|
Metabolism: carbohydrate metabolism: glycolysis/gluconeogenesis enzymes
|
|
| Glycolysis |
- Hexokinase (HK1, HK2, HK3, Glucokinase)→/Glucose 6-phosphatase←
- Glucose isomerase
- Phosphofructokinase 1 (Liver, Muscle, Platelet)→/Fructose 1,6-bisphosphatase←
|
|
- Fructose-bisphosphate aldolase (Aldolase A, B, C)
- Triosephosphate isomerase
|
|
- Glyceraldehyde 3-phosphate dehydrogenase
- Phosphoglycerate kinase
- Phosphoglycerate mutase
- Enolase
- Pyruvate kinase (PKLR, PKM2)
|
|
|
| Gluconeogenesis only |
| to oxaloacetate: |
- Pyruvate carboxylase
- Phosphoenolpyruvate carboxykinase
|
|
| from lactate (Cori cycle): |
|
|
| from alanine (Alanine cycle): |
|
|
| from glycerol: |
- Glycerol kinase
- Glycerol dehydrogenase
|
|
|
| Regulatory |
- Fructose 6-P,2-kinase:fructose 2,6-bisphosphatase
- PFKFB1, PFKFB2, PFKFB3, PFKFB4
- Bisphosphoglycerate mutase
|
|
Hydrolase: esterases (EC 3.1)
|
|
3.1.1: Carboxylic
ester hydrolases |
- Cholinesterase
- Acetylcholinesterase
- Butyrylcholinesterase
- Pectinesterase
- 6-phosphogluconolactonase
- PAF acetylhydrolase
- Lipase
- Bile salt-dependent
- Gastric/Lingual
- Pancreatic
- Lysosomal
- Hormone-sensitive
- Endothelial
- Hepatic
- Lipoprotein
- Monoacylglycerol
- Diacylglycerol
|
|
| 3.1.2: Thioesterase |
- Palmitoyl protein thioesterase
- Ubiquitin carboxy-terminal hydrolase L1
- 4-hydroxybenzoyl-CoA thioesterase
|
|
| 3.1.3: Phosphatase |
- Alkaline phosphatase
- Acid phosphatase (Prostatic)/Tartrate-resistant acid phosphatase/Purple acid phosphatases
- Nucleotidase
- Glucose 6-phosphatase
- Fructose 1,6-bisphosphatase
- Protein phosphatase
- OCRL
- Pyruvate dehydrogenase phosphatase
- Fructose 6-P,2-kinase:fructose 2,6-bisphosphatase
- PTEN
- Phytase
- Inositol-phosphate phosphatase
- Protein phosphatase: Protein tyrosine phosphatase
- Protein serine/threonine phosphatase
- Dual-specificity phosphatase
|
|
3.1.4:
Phosphodiesterase |
- Autotaxin
- Phospholipase
- Sphingomyelin phosphodiesterase
- PDE1
- PDE2
- PDE3
- PDE4A/PDE4B
- PDE5
- Lecithinase (Clostridium perfringens alpha toxin)
- Cyclic nucleotide phosphodiesterase
|
|
| 3.1.6: Sulfatase |
- arylsulfatase
- Arylsulfatase A
- Arylsulfatase B
- Arylsulfatase E
- Steroid sulfatase
- Galactosamine-6 sulfatase
- Iduronate-2-sulfatase
- N-acetylglucosamine-6-sulfatase
|
|
Nuclease (includes
deoxyribonuclease
and ribonuclease) |
3.1.11-16:
Exonuclease |
| Exodeoxyribonuclease |
|
|
| Exoribonuclease |
|
|
|
3.1.21-31:
Endonuclease |
| Endodeoxyribonuclease |
- Deoxyribonuclease I
- Deoxyribonuclease II
- Deoxyribonuclease IV
- Restriction enzyme
- UvrABC endonuclease
|
|
| Endoribonuclease |
- RNase III
- RNase H
- RNase P
- RNase A
- RNase T1
- RNA-induced silencing complex
|
|
| either deoxy- or ribo- |
- Aspergillus nuclease S1
- Micrococcal nuclease
|
|
|
|
Transferases: phosphorus-containing groups (EC 2.7)
|
|
2.7.1-2.7.4:
phosphotransferase/kinase
(PO4) |
| 2.7.1: OH acceptor |
- Hexo-
- Gluco-
- Fructo-
- Galacto-
- Phosphofructo-
- 1
- Liver
- Muscle
- Platelet
- 2
- Riboflavin
- Shikimate
- Thymidine
- NAD+
- Glycerol
- Pantothenate
- Mevalonate
- Pyruvate
- Deoxycytidine
- PFP
- Diacylglycerol
- Phosphoinositide 3
- Class I PI 3
- Class II PI 3
- Sphingosine
- Glucose-1,6-bisphosphate synthase
|
|
| 2.7.2: COOH acceptor |
- Phosphoglycerate
- Aspartate kinase
|
|
| 2.7.3: N acceptor |
|
|
| 2.7.4: PO4 acceptor |
- Phosphomevalonate
- Adenylate
- Nucleoside-diphosphate
- Uridylate
- Guanylate
- Thiamine-diphosphate
|
|
|
2.7.6: diphosphotransferase
(P2O7) |
- Ribose-phosphate diphosphokinase
- Thiamine diphosphokinase
|
|
2.7.7: nucleotidyltransferase
(PO4-nucleoside) |
| Polymerase |
| DNA polymerase |
- DNA-directed DNA polymerase
- I
- II
- III
- IV
- V
- RNA-directed DNA polymerase
- Reverse transcriptase
- Telomerase
- DNA nucleotidylexotransferase/Terminal deoxynucleotidyl transferase
|
|
| RNA nucleotidyltransferase |
- RNA polymerase/DNA-directed RNA polymerase
- RNA polymerase I
- RNA polymerase II
- RNA polymerase III
- RNA polymerase IV
- Primase
- RNA-dependent RNA polymerase
- PNPase
|
|
|
Phosphorolytic
3' to 5' exoribonuclease |
|
|
| Nucleotidyltransferase |
- UTP—glucose-1-phosphate uridylyltransferase
- Galactose-1-phosphate uridylyltransferase
|
|
| Guanylyltransferase |
|
|
| Other |
- Recombinase (Integrase)
- Transposase
|
|
|
| 2.7.8: miscellaneous |
| Phosphatidyltransferases |
- CDP-diacylglycerol—glycerol-3-phosphate 3-phosphatidyltransferase
- CDP-diacylglycerol—serine O-phosphatidyltransferase
- CDP-diacylglycerol—inositol 3-phosphatidyltransferase
- CDP-diacylglycerol—choline O-phosphatidyltransferase
|
|
| Glycosyl-1-phosphotransferase |
- N-acetylglucosamine-1-phosphate transferase
|
|
|
2.7.10-2.7.13: protein kinase
(PO4; protein acceptor) |
| 2.7.10: protein-tyrosine |
|
|
| 2.7.11: protein-serine/threonine |
- see serine/threonine-specific protein kinases
|
|
| 2.7.12: protein-dual-specificity |
- see serine/threonine-specific protein kinases
|
|
| 2.7.13: protein-histidine |
- Protein-histidine pros-kinase
- Protein-histidine tele-kinase
- Histidine kinase
|
|
|
Enzymes
|
|
| Activity |
- Active site
- Binding site
- Catalytic triad
- Oxyanion hole
- Enzyme promiscuity
- Catalytically perfect enzyme
- Coenzyme
- Cofactor
- Enzyme catalysis
|
|
| Regulation |
- Allosteric regulation
- Cooperativity
- Enzyme inhibitor
|
|
| Classification |
- EC number
- Enzyme superfamily
- Enzyme family
- List of enzymes
|
|
| Kinetics |
- Enzyme kinetics
- Eadie–Hofstee diagram
- Hanes–Woolf plot
- Lineweaver–Burk plot
- Michaelis–Menten kinetics
|
|
| Types |
- EC1 Oxidoreductases (list)
- EC2 Transferases (list)
- EC3 Hydrolases (list)
- EC4 Lyases (list)
- EC5 Isomerases (list)
- EC6 Ligases (list)
|