Cofactors

There are no Cofactors for this Enzyme

Reaction Mechanism

fructose-bisphosphatase By Reference

Fructose 1,6-bisphosphatase (FBPase) hydrolyses fructose 1,6-bis-phosphate to fructose 6-phosphate and phosphate. The enzyme plays a crucial role in gluconeogenesis, the formation of glucose from non-carbohydrate carbon containing substrates. The enzyme is only capable of catalysing the forward reaction, while phosphofructokinase catalyses the reverse reaction. Regulation of the two enzyme is performed by metabolites such as fructose 2,6 bis-phosphate, ensuring that enhances reactivity of one enzyme is accompanied by suppressed reactivity of the other.




• Summary
• Step 1
• Step 2
• Step 3
• Step 4
• Products

There are three divalent metal cations present within the catalytic site. Mg(2+) at site one is directly coordinated to the 1-(OH) of the 6 fructose phosphate product as a fifth coordinating ligand. The cation is thought to stabilise the negative charge of the hydroxide group before the transfer of a proton from Asp68, which relays a proton from the substrate neutralises the product. The second metal coordinates to a nucleophilic water molecule, also polarised through hydrogen bonds to Asp74 and Glu98, which abstracts a proton from a second coordinated water. The resulting hydroxide ion is the attacking nucleophile, displacing the 6 fructose phosphate in an S_N2 mechanism. The resulting oxide is protonated as stated above.

Catalytic Residues

AA	Uniprot	Uniprot Resid	PDB	PDB Resid
Asp	P00636	122	1eyi	121
Glu	P00636	98	1eyi	97
Asp	P00636	69	1eyi	68
Asp	P00636	75	1eyi	74
Asp	P00636	119	1eyi	118
Leu	P00636	121	1eyi	120
Glu	P00636	281	1eyi	280
Glu	P00636	99	1eyi	98

Step Components

inferred reaction step, native state of enzyme regenerated, proton transfer, overall product formed



Step 1.

Asp74 abstracts a proton from the catalytic water, which attacks the metal bound phosphate and eliminates the F6P as a negatively charged intermediate in an S_N2-type reaction. It is likely that the reaction proceeds via a pentavalent transition state.



Step 2.

Asp68 abstracts the proton from the phosphate group,



Step 3.

F6P abstracts the proton from Asp68 to generate the final product.



Step 4.

Inferred return step. Asp74 returns a proton to water, which is then transferred to bulk solvent.



Products.

The products of the reaction.

View Reaction Mechanisms in M-CSA

Reaction Parameters

• Kinetic Parameters

  Organism	KM Value [mM]	Substrate	Comment
  Synechocystis sp.	0.21	D-fructose 1,6-bisphosphate	mutant R176A, pH 8.0, 28°C
  Euglena gracilis	0.49	D-fructose 1,6-bisphosphate	isozyme EgFBPaseII, pH 8.0, temperature not specified in the publication
  Lactobacillus delbrueckii subsp. lactis	0.6	beta-D-glucose 1,6-bisphosphate	mutant enzyme H20A, in 50 mM K+HEPES pH 7.0 at 25°C
  Sulfurisphaera tokodaii	7.2	D-fructose 1,6-bisphosphate	pH 7.8, 48°C, mutant enzyme Y348F
  Bacillus methanolicus	8.8	D-fructose 1,6-bisphosphate	pH 7.7, 50°

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• Temperature

  Organism	Temperature Range	Comment
  Clonorchis sinensis	15 - 45	more than 70% of maxiumum activity
  Pisum sativum	30 - 70	30°C: about 40% of maximal activity, 70°C: about 60% of maximal activity
  Thermococcus kodakarensis	37 - 95	the enzyme shows a nearly linear increase in activity between 37°C and 95°C

• pH

  Organism	pH Range	Comment
  Pisum sativum	5.5 - 7.5	pH 5.5: about 20% of maximal activity, pH 7.5: about 25% of maximal activity
  Euglena gracilis	6 - 9	activity range, profile overview, recombinant enzyme
  Saccharomyces cerevisiae	6 - 11	pH 6.0: about 25% of maximal activity, pH 11.0.: 55% of maximal activity
  Pelophylax lessonae	6 - 9.5	activity range
  Bos taurus	6.3 - 10	pH 6.3: about 30% of maximal activity, pH 10.0: about 45% of maximal activity

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Associated Proteins

Citations

• Phosphofructokinase-1 and fructose bisphosphatase-1 in canine liver and kidney.
• Metabolic regulation of calcium pumps in pancreatic cancer: role of phosphofructokinase-fructose-bisphosphatase-3 (PFKFB3).
• Fructose bisphosphatase 2 overexpression increases glucose uptake in skeletal muscle.
• Novel fructose bisphosphatase 1 gene mutation presenting as recurrent episodes of vomiting in an Indian child.
• Transforming growth factor β1 upregulates 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase-4 expression in A549 and MCF-10A cells.
• Come, Sweet Death: Why Endothelial Cells Die in Fructose.
• Viral infections inhibit saponin biosynthesis and photosynthesis in Panax notoginseng.
• A novel variant in the FBP1 gene causes fructose-1,6-bisphosphatase deficiency through increased ubiquitination.
• Role of PFKFB3-driven glycolysis in sepsis.
• Weak neuronal glycolysis sustains cognition and organismal fitness
• Beet leaf (beta vulgaris L.) extract attenuates iron-induced testicular toxicity: Experimental and computational approach.