What Is 2-phospho-D-glycerate hydro-lyase

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Last updated: April 15, 2026

Quick Answer: 2-phospho-D-glycerate hydro-lyase, also known as enolase, is an enzyme that catalyzes the conversion of 2-phosphoglycerate (2-PG) to phosphoenolpyruvate (PEP) in glycolysis. This reaction is reversible and essential for energy production, occurring in nearly all organisms. The enzyme typically functions as a homodimer with a molecular weight of approximately 94 kDa.

Key Facts

Enolase catalyzes the ninth step of glycolysis, converting 2-phosphoglycerate to phosphoenolpyruvate.
The reaction removes a water molecule, making it a dehydration process classified as a hydro-lyase (EC 4.2.1.11).
Human enolase has three isozymes: alpha (general), beta (muscle), and gamma (neuronal).
The optimal pH for enolase activity is between 7.0 and 7.5, depending on the organism.
Enolase is inhibited by fluoride ions, which form a complex with phosphate and magnesium at the active site.

Overview

2-phospho-D-glycerate hydro-lyase, commonly referred to as enolase, is a critical enzyme in the glycolytic pathway responsible for energy production in cells. It facilitates the reversible dehydration of 2-phosphoglycerate (2-PG) to form phosphoenolpyruvate (PEP), a high-energy compound used in ATP synthesis.

Enolase is present in nearly all forms of life, from bacteria to humans, highlighting its evolutionary conservation. The enzyme requires a divalent metal ion, typically Mg²⁺, for catalytic activity and functions optimally under neutral pH conditions.

Substrate specificity: Enolase acts exclusively on 2-phospho-D-glycerate, converting it into phosphoenolpyruvate through a stereospecific reaction.
Enzyme class: It belongs to the hydro-lyase family (EC 4.2.1.11), which cleaves carbon-oxygen bonds via elimination rather than hydrolysis.
Structure: Most enolases function as homodimers, with each subunit weighing approximately 47 kDa, totaling ~94 kDa.
Gene location: In humans, the alpha-enolase gene (ENO1) is located on chromosome 1p36, a region linked to several cancers.
Expression: Enolase is highly expressed in tissues with high glycolytic demand, such as brain, muscle, and rapidly dividing cancer cells.

How It Works

The enzymatic mechanism of 2-phospho-D-glycerate hydro-lyase involves precise coordination of metal ions and amino acid residues to facilitate dehydration. The reaction proceeds through an enolate intermediate stabilized by the enzyme's active site.

Active site residues:Lys345 and Glu211 in human enolase are critical for proton abstraction and stabilization of the transition state.
Metal ion dependence:Two Mg²⁺ ions are required—one for substrate binding and another for catalysis—enhancing reaction efficiency by over 100,000-fold.
Reaction mechanism: The enzyme removes a water molecule from 2-PG, forming PEP, which contains a high-energy phosphate bond used in ATP generation.
Reversibility: The reaction is reversible, allowing enolase to function in both glycolysis and gluconeogenesis depending on cellular energy needs.
Inhibition:Fluoride inhibits enolase by forming a fluoro-phosphate complex with inorganic phosphate, blocking the active site.
Temperature sensitivity: Enolase activity declines sharply above 45°C, with complete denaturation occurring around 60°C in mammalian forms.

Comparison at a Glance

Enolase variants across species and isozymes exhibit differences in structure, function, and expression patterns.

Feature	Human Alpha-Enolase	Yeast Enolase	Bacterial Enolase	Gamma-Enolase (Neuron-Specific)
Gene	ENO1	ENO1	eno	ENO2
Molecular Weight	94 kDa (dimer)	90 kDa	88 kDa	94 kDa
Optimal pH	7.0–7.5	6.8–7.2	7.0	7.2
Tissue Expression	Ubiquitous	Cytoplasmic	Universal	Neurons, neuroendocrine cells
Special Functions	Role in hypoxia response	Essential for fermentation	Virulence factor in pathogens	Neuroprotection, stress response

The table illustrates functional diversity despite structural conservation. Bacterial enolase, for example, can act as a surface receptor in pathogens like Streptococcus pneumoniae, aiding immune evasion. In contrast, gamma-enolase serves as a biomarker for neuroendocrine tumors and neuronal damage, detectable in cerebrospinal fluid. These variations underscore enolase’s dual roles in metabolism and cellular signaling.

Why It Matters

Understanding 2-phospho-D-glycerate hydro-lyase is vital for insights into cellular metabolism, disease mechanisms, and therapeutic development. Its central role in glycolysis makes it a target for cancer and antimicrobial research.

Cancer metabolism: Tumor cells upregulate enolase to support aerobic glycolysis (Warburg effect), increasing glucose consumption.
Diagnostic marker: Elevated levels of gamma-enolase (NSE) in serum correlate with small cell lung cancer and neuroblastoma.
Autoimmune disease: Alpha-enolase is a target in anti-phospholipid syndrome and some forms of lupus.
Antibiotic target: Bacterial enolase is being explored for novel antimicrobial drugs due to its essential metabolic role.
Neurodegeneration: Misfolded enolase has been linked to Alzheimer’s disease pathology and synaptic dysfunction.
Evolutionary insight: High sequence conservation across over 2 billion years highlights its fundamental role in life.

From energy production to disease diagnostics, enolase exemplifies how a single enzyme can influence multiple biological domains. Its study continues to yield insights into both basic biochemistry and clinical medicine.