{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption=
{{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption=
{{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption=
{{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption=
{{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption={{{!}} align="center" border="0"
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Enzyme
{{!}} Enolase
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PDB Code
{{!}} {{PDB|2ONE}}
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Organism
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YeastYeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with about 1,500 species currently described; they dominate fungal diversity in the oceans. Most reproduce asexually by budding, although a few do so by binary fission...
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Complexed molecules
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2-phosphoglycerate2-Phosphoglyceric acid , or 2-phosphoglycerate, is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate , the penultimate step in the conversion of glucose to pyruvate.-In Glycolysis: -References:...
and
phosphoenolpyruvatePhosphoenolpyruvic acid , or phosphoenolpyruvate as the anion, is an important chemical compound in biochemistry. It has the high-energy phosphate bond found in living organisms, and is involved in glycolysis and gluconeogenesis...
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|Alternative_products=
|Catalytic_activity=
|Cofactors=
|Enzyme_regulation=
|Diseases=
|Pharmaceuticals=
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Enolase, also known as phosphopyruvate dehydratase, is a metalloenzyme responsible for the catalysis of
2-phosphoglycerate2-Phosphoglyceric acid , or 2-phosphoglycerate, is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate , the penultimate step in the conversion of glucose to pyruvate.-In Glycolysis: -References:...
(2-PG) to
phosphoenolpyruvatePhosphoenolpyruvic acid , or phosphoenolpyruvate as the anion, is an important chemical compound in biochemistry. It has the high-energy phosphate bond found in living organisms, and is involved in glycolysis and gluconeogenesis...
(PEP), the ninth and penultimate step of
glycolysisGlycolysis is the metabolic pathway that converts glucose, C
6H
12O
6, into pyruvate, C
3H
6O
3-...
.
{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption=
{{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption=
{{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption=
{{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption=
{{Protbox
|Name=Enolase
|Photo=Enolase 2ONE wpmp.png
|Caption={{{!}} align="center" border="0"
{{!}}
Enzyme
{{!}} Enolase
{{!}}-
{{!}}
PDB Code
{{!}} {{PDB|2ONE}}
{{!}}-
{{!}}
Organism
{{!}}
YeastYeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with about 1,500 species currently described; they dominate fungal diversity in the oceans. Most reproduce asexually by budding, although a few do so by binary fission...
{{!}}-
{{!}}
Complexed molecules
{{!}}
2-phosphoglycerate2-Phosphoglyceric acid , or 2-phosphoglycerate, is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate , the penultimate step in the conversion of glucose to pyruvate.-In Glycolysis: -References:...
and
phosphoenolpyruvatePhosphoenolpyruvic acid , or phosphoenolpyruvate as the anion, is an important chemical compound in biochemistry. It has the high-energy phosphate bond found in living organisms, and is involved in glycolysis and gluconeogenesis...
{{!}}}
|Gene_type=
|Molecular_weight=
|Structure=
|Type=
|Functions=
|Domains=
|Motifs=
|Alternative_products=
|Catalytic_activity=
|Cofactors=
|Enzyme_regulation=
|Diseases=
|Pharmaceuticals=
|Taxa=
|Cells=
|Location=
|Names=
|Pathways=
|Interactions=
|Pages=
|Review=
}}
Enolase, also known as phosphopyruvate dehydratase, is a metalloenzyme responsible for the catalysis of
2-phosphoglycerate2-Phosphoglyceric acid , or 2-phosphoglycerate, is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate , the penultimate step in the conversion of glucose to pyruvate.-In Glycolysis: -References:...
(2-PG) to
phosphoenolpyruvatePhosphoenolpyruvic acid , or phosphoenolpyruvate as the anion, is an important chemical compound in biochemistry. It has the high-energy phosphate bond found in living organisms, and is involved in glycolysis and gluconeogenesis...
(PEP), the ninth and penultimate step of
glycolysisGlycolysis is the metabolic pathway that converts glucose, C
6H
12O
6, into pyruvate, C
3H
6O
3-...
. Enolase can also catalyze the reverse reaction, depending on environmental concentrations of substrates. The optimum pH for this enzyme is 6.5. Enolase is present in all tissues and organisms capable of glycolysis or
fermentationFermentation is the process of deriving energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. This is in contrast to cellular respiration, where electrons are donated to an exogenous electron acceptor,...
. The enzyme was discovered by Lohmann and
MeyerhofOtto Fritz Meyerhof was a German-born physician and biochemist.-Biography:Meyerhof was born in Hanover, the son of wealthy Jewish parents. He spent most of his childhood in Berlin, where he started his study of medicine...
in 1934, and has since been isolated from a variety of sources including human muscle and erythrocytes. There are three subunits of enolase, α, β, and γ, which can combine to form five different isoenzymes: αα, αβ, αγ, ββ, and γγ. Three of these isoenzymes are more commonly found in adult human cells than the others:
- αα or non-neuronal enolase (NNE), which is found in a variety of tissues, including liver, brain, kidney, spleen, adipose. Also known as enolase 1
- ββ or muscle specific enolase (MSE). Also known as enolase 3.
- γγ or neuron-specific enolase (NSE). Also known as enolase 2
Enolase 2 , also known as ENO2 and neuron-specific enolase , is a human gene. It makes a phosphopyruvate hydratase....
.
Structure
Enolase has a molecular weight of 82,000-100,000 Daltons depending on the isoform. In human alpha enolase, the two subunits are
antiparallelThe term antiparallel may refer to:*Antiparallel , the orientation of adjacent molecules*Antiparallel , the placement of parallel lines in relation to an angle*Antiparallel , the polarity of devices run in parallel...
in orientation so that Glu
20 of one subunit forms an ionic bond with
ArgArginine is an α-amino acid. The
L-form is one of the 20 most common natural amino acids. Its codons are CGU, CGC, CGA, CGG, AGA, and AGG. In mammals, arginine is classified as a semiessential or conditionally essential amino acid, depending on the developmental stage and health...
414 of the other subunit. Each subunit has two distinct domains. The smaller N-terminal domain consists of three
α-helicesA common motif in the secondary structure of proteins, the alpha helix is a right- or left-handed coiled conformation, resembling a spring, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...
and four
β-sheetsThe β sheet is the second form of regular secondary structure in proteins consisting of beta strands connected laterally by five or more hydrogen bonds, forming a generally twisted, pleated sheet...
. The larger C-terminal domain starts with two β-sheets followed by two α-helices and ends with a barrel comprised of alternating β-sheets and α-helices arranged so that the β-beta sheets are surrounded by the α-helices. The enzyme’s compact, globular structure results from significant hydrophobic interactions between these two domains.
Enolase is a highly conserved enzyme with five active-site residues being especially important for activity. When compared to wild-type enolase, a mutant enolase that differs at either the Glu
168, Glu
211,
LysLysine is an α-amino acid with the chemical formula HO
2CCH
4NH
2. This amino acid is an essential amino acid, which means that humans cannot synthesize it. Its codons are AAA and AAG.Lysine is a base, as are arginine and histidine...
345, or Lys
396 residue has an activity level that is cut by a factor of 105. Also, changes affecting
HisHistidine is one of the 20 standard amino acids present in proteins. Nutritionally, histidine is considered an essential amino acid in human infants. After reaching several years of age, humans begin to synthesize it and it thus becomes a non-essential amino acid...
159 leave the mutant with only 0.01% of its catalytic activity. An integral part of enolase are two Mg
2+ cofactors in the active site, which serve to stabilize negative charges in the substrate.
Mechanism
Using isotopic probes, the overall mechanism for converting 2-PG to PEP is proposed to be an Elcb elimination reaction involving a carbanion intermediate. The following detailed mechanism is based on studies of crystal structure and
kineticsChemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition...
. When the substrate, 2-phosphoglycerate, binds to α-enolase, its carboxyl group coordinates with two magnesium ion cofactors in the active site. This stabilizes the negative charge on the deprotonated oxygen while increasing the acidity of the alpha hydrogen. Enolase’s Lys
345 deprotonates the alpha hydrogen, and the resulting negative charge is stabilized by resonance to the carboxylate oxygen and by the magnesium ion cofactors. Following the creation of the carbanion intermediate, the hydroxide on C3 is eliminated as water with the help of Glu
211, and PEP is formed.
Additionally, conformational changes occur within the enzyme that aid catalysis. In human α-enolase, the substrate is rotated into position upon binding to the enzyme due to interactions with the two catalytic magnesium ions,
GlnGlutamine is one of the 20 amino acids encoded by the standard genetic code. Its side chain is an amide formed by replacing the side-chain hydroxyl of glutamic acid with an amine functional group. It can therefore be considered the amide of glutamic acid. Its codons are CAA and CAG. Glutamine is...
167, and Lys
396. Movements of loops
SerSerine is an organic compound with the formula HO
2CCHCH
2OH.-Occurrence:...
36 to His
43, Ser
158 to
GlyGlycine is an organic compound with the formula NH2CH2COOH. With only a hydrogen atom as its side chain, glycine is the smallest of the 20 amino acids commonly found in proteins....
162, and Asp
255 to
AsnAsparagine is one of the 20 most common natural amino acids on Earth. It has carboxamide as the side chain's functional group. It is not an essential amino acid...
256 allow Ser
39 to coordinate with Mg
2+ and close off the active site. In addition to coordination with the catalytic magnesium ions, the pKa of the substrate’s alpha hydrogen is also lowered due to protonation of the phosphoryl group by His
159 and its proximity to Arg
374. Arg
374 also causes Lys
345 in the active site to become deprotonated, which primes Lys
345 for its role in the mechanism.
Diagnostic Uses
In recent medical experiments, enolase concentrations have been sampled in an attempt to diagnose certain conditions and their severity. For example, higher concentrations of enolase in
cerebrospinal fluidCerebrospinal fluid , Liquor cerebrospinalis, is a clear bodily fluid that occupies the subarachnoid space and the ventricular system around and inside the brain. In essence, the brain "floats" in it....
more strongly correlated to low-grade
astrocytomaAstrocytomas are cancers of the brain that originate in star-shaped brain cells called astrocytes.They account for roughly 75% of neuroepithelial tumors.-Grading:...
than did other enzymes tested (
aldolaseAldolase A is an enzyme which catalyses one of the aldol reactions: The substrate, fructose 1,6-bisphosphate is broken down into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate . This reaction is a part of glycolysis. Three aldolase isozymes , encoded by three different genes, are...
,
pyruvate kinasePyruvate kinase is an enzyme involved in glycolysis. It catalyzes the transfer of a phosphate group from phosphoenolpyruvate to ADP, yielding one molecule of pyruvate and one molecule of ATP.-Reaction:The reaction with pyruvate kinase:...
,
creatine kinaseCreatine kinase , also known as creatine phosphokinase or phospho-creatine kinase or sometimes wrongfully also creatinine kinase, is an enzyme expressed by various tissues and cell types. CK catalyses the conversion of creatine and consumes adenosine triphosphate to create phosphocreatine and...
, and
lactate dehydrogenaseLactate dehydrogenase is an enzyme present in a wide variety of organisms, including plants and animals.Lactate dehydrogenases exist in four distinct enzyme classes. Two of them are cytochrome c-dependent enzymes with each acting on either D-lactate or L-lactate...
). The same study showed that the fastest rate of tumor growth occurred in patients with the highest levels of CSF enolase.
Increased levels of enolase have also been identified in patients who have suffered a recent
myocardial infarctionMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, is the interruption of blood supply to part of the heart, causing some heart cells to die...
or cerebrovascular accident. It has been inferred that levels of CSF neuron-specific enolase,
serumBlood plasma is the yellow liquid component of blood, in which the blood cells in whole blood would normally be suspended. It makes up about 55% of the total blood volume. It is mostly water and contains dissolved proteins, glucose, clotting factors, mineral ions, hormones and carbon dioxide...
NSE, and creatine kinase (type BB) are indicative in the prognostic assessment of cardiac arrest victims. Other studies have focused on the prognostic value of NSE values in cerebrovascular accident victims.
Autoantibodies to alpha-enolase are associated with the rare syndrome called
Hashimoto's encephalopathyHashimoto's Encephalopathy is a very rare condition associated with Hashimoto's Thyroiditis. Hashimoto's Encephalopathy is a neuroendocrine disorder. Thyroid antibodies in the disease are increased but do not correlate with the severity...
.
Fluoride Inhibition
FluorideFluoride is the anion F
−, the reduced form of fluorine. Both organic and inorganic compounds containing the element fluorine are sometimes called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are distinct relative to other...
is a known competitor of enolase’s substrate, 2-PG. The fluoride is part of a complex with magnesium and phosphate, which binds in the active site instead of 2-PG. As such, drinking
fluoridated waterWater fluoridation is the controlled addition of fluoride to a public water supply to reduce tooth decay. Fluoridated water has fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride...
provides fluoride at a level which inhibits oral bacteria enolase activity without harming humans. Disruption of the bacteria’s glycolytic pathway, and thus, its normal metabolic functioning prevents
dental cariesDental caries, also known as tooth decay or cavity, is a disease wherein bacterial processes damage hard tooth structure . These tissues progressively break down, producing dental cavities . Two groups of bacteria are responsible for initiating caries: Streptococcus mutans and Lactobacilli...
from forming.