Cholinesterases multiple molecular forms

Cholinesterases are subdivided into acetylcholinesterase and cholinesterase, one with a narrow, the other with broad substrate specificity [109-112], Both enzymes exist in multiple molecular forms distinguishable by their subunits association (Fig. 2.4). The hydrodynamic properties of these associations have allowed globular (G) and asymmetric (A) forms to be distinguished. The G forms can be hydrophilic (water-soluble, and excreted into body fluids) or amphiphilic (membrane-bound). The homomeric class exists... 

Figure 1 Subunit structure of the multiple molecular forms of ChEs. G, globular forms A, asymmetric forms with collagen-like tails. Each circle is a catalytic subunit disulfide bridges indicated by S-S as found in the electric organ of the electric eel. (Modified from Brimijoin WS (1992) US EPA Workshop on Cholinesterase Methodologies.)...

Modern techniques for protein separation have been used to demonstrate the existence of multiple molecular forms of cholinesterase. Such entities, which are groups of isoenzymes, can be separated either by electrophoresis or by chromatography (H8) moreover, they can be distinguished by kinetic means (e.g., R3). 

Multiple Molecular Forms of Human Plasma Cholinesterase... 

The classic view of two cholinesterases whose sole function is to terminate cholinergic signals at the synapse has been repeatedly challenged by observations that were incongruent with this view and suggested a far more complex picture of multiple molecular forms with distinct temporal and spatial expression patterns. This complexity mainly results from alternative splicing... 

Aggregation of enzyme molecules with each other or with nonenzymatic proteins may give rise to multiple forms that can be separated by techniques that depend on differences in molecular size. For example, four catalytically active cholinesterase components with molecular weights ranging from about 80,000 to 340,000 are found in most sera, with the heaviest component, C4, contributing most of the enzyme activity. Other enzyme forms are also occasionally present, but it appears that the principal serum cholinesterase fractions can be attributed to different states of aggregation of a single monomer. 

L12. LaMotta, R. V., Woronick, C. L., and Reinfrank, R. F., Multiple forms of serum cholinesterase Molecular weights of the isoenzymes. Arch. Biochem. Biophys. 136, 448-451 (1970). 

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