Characterization of serum cholinesterase in familial hyper-cholinesterasemia associated with an isozyme variant band.

An investigation of the properties and kinetics of serum cholinesterase (chE) was conducted in familial cases of serum hyper-chE activity. An inhibition study with specific pseudo-chE inhibitor (ethopropazine), or with anti-human pseudo-chE sera, has produced evidence that this genetically variant chE is pseudo-chE. The Km or relative activity of the variant chE against enzyme protein turns out to be the same as that of the normal serum chE. However, the variant serum chE shows more basic pK in addition to the main pK of the normal pseudo-chE on isoelectrofocusing analysis. The serum chE isozyme analysis has revealed two different extrabands in the variant: one demonstrated as a sharp line between bands 3 and 4, which we described previously, and the other as slow migrating broad band in the cathodic region close to the origin. Both prove to be pseudo-chE. Although there have been some similar descriptions about the latter type of extraband, no reports are found about the former type. It is noteworthy that the use of heparin as an anti-coagulant caused the total disappearance of the first type of extraband. It should be remembered that only heparinized plasma was used in the earlier studies. Since the detection of the former type of band seems to be specific and is simple, our findings would probably help clinicians diagnose a familial case of hyper-chE.