enolase-1; alpha enolase; phosphopyruvate hydratase; C-myc promoter-binding protein; plasminogen-binding protein (ENO1, ENO1L1, MBPB1, MPB1)
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Introduction
Formerly phosphopyruvate hydratase
Function
- multifunctional enzyme
- role in glycolysis
- role in growth control, hypoxia tolerance & allergy
- role in intravascular & pericellular fibrinolytic system due to its ability to serve as a receptor & activator of plasminogen on the cell surface of several cell-types including leukocytes & neurons (putative)
- binds to the c-myc promoter & acts as a transcriptional repressor
- may be a tumor suppressor
- ENO1 interacts with PLG in the neuronal plasma membrane & promotes its activation; C-terminal lysine is required for binding
- carbohydrate degradation, glycolysis, pyruvate from D-glyceraldehyde 3-phosphate: step 4/5
2-phospho-D-glycerate <--> phosphoenolpyruvate + H2O
Cofactor:
- Mg+2, required for catalysis & for stabilizing the dimer
Structure
- belongs to the enolase family
- mammalian enolase is composed of 3 isozyme subunits, alpha, beta & gamma, which can form homodimers or heterodimers which are cell-type & development-specific
Compartment
- cytoplasm, cell membrane, myofibril, sarcomere, M-band
- can translocate to the plasma membrane in either the homodimeric (alpha/alpha) or heterodimeric (alpha/gamma) form
- localized to the M-band
- isoform MBP-1: nucleus
Alternative initiation
- named isoforms=2
Expression
- alpha/alpha homodimer is expressed in embryo & in most adult tissues
- alpha/beta heterodimer & beta/beta homodimer are found in striated muscle
- the alpha/gamma heterodimer & the gamma/gamma homodimer are found in neurons
- during ontogenesis, there is a transition from the alpha/alpha homodimer to the alpha/beta heterodimer in striated muscle cells, & to the alpha/gamma heterodimer in nerve cells
Pathology
- induced in diffuse large cell lymphoma (DLCL) after treatment with the natural biological agent, Bryo1
- ENO1 is identified as an autoantigen in Hashimoto encephalopathy
- antibodies against alpha-enolase are present in sera from patients with cancer-associated retinopathy syndrome (CAR)
- used as a diagnostic marker for many tumors
- in the heterodimeric form, alpha/gamma, as a marker for hypoxic brain injury after cardiac arrest
- marker for endometriosis
Genetics
- may be encoded by same gene that encodes tau crystallin