Acetylcholinesterase from human erythrocytes

General description

Acetylcholinesterase (AChE) belongs to the carboxyl esterase family of enzymes. The erythrocyte AChE is membrane bound. AChE is mapped to human chromosome 7q22.1. It is enriched in aged erythrocytes.

Predominantly exists as a tetrameric glycoprotein composed of disulfide-linked homodimers with a monomer MW of ~80 kDa.

Application

Acetylcholinesterase (AChE) from Sigma has been used in the structure-activity study of phosphoramido acid esters as inhibitors of AChE.

Acetylcholinesterase from human erythrocytes has been used in:

• cholinesterase inhibition assay for screening 4-aminoquinoline based compounds
• AChE activity assays to test the effect of positive allosteric modulators (PAMs)
• organophosphorus compounds based inhibition assay

Biochem/physiol Actions

Acetylcholinesterase (AChE) is regarded as a biomarker in neurotoxicity. It is a modulator of nitric oxide signal transduction pathway and marker of membrane integrity and aging. The levels of erythrocyte (RBC) AChE are affected on pesticide exposure and in hemolytic anemia. RBC AChE is a marker in Hirschsprung′s disease and inflammation.

Acetylcholinesterase is the major in vivo degradative enzyme for acetylcholine. It converts acetylcholine and water to choline and acetic acid. Cholinesterases are inhibited by the natural carbamate alkaloid, eserine or physostigmine.

In blood there are two cholinesterases present: The erythrocyte associated enzyme, which is a true cholinesterase or acetylcholinesterase [(AChE) - E.C. 3.1.1.7], the serum associated enzyme, which is Pseudocholinesterase or Butyrylcholinesterase [(BuChE) - EC 3.1.1.8].
AChE is an ectoenzyme, anchored to the erythrocyte membrane via a GPI moiety.

Unit Definition

One unit will hydrolyze 1.0 μmole of acetylthiocholine iodide per min at pH 7.4 at 37 °C.

Physical form

Solution in 20 mM HEPES, pH 8.0, containing 0.1% TRITON® X-100

Preparation Note

The enzyme is the amphiphilic form extracted together with its GPI anchor with the aid of TRITON X-100 and purified by affinity chromatography.

Analysis Note

The activity obtained using acetylcholine as substrate is 30-100 times that obtained with butyrylcholine, using acetylcholinesterase from electric eel.