Rapid heterolysis of indophenyl acetate by a constituent of a preparation of horse serum cholinesterase.

The researchers found a short-lived reaction phase when the commercial compound of horse serum cholinesterase breaks down indophenyl acetate, which is not caused the by the serum cholinesterase enzyme but another main component of the preparation. This component, tentatively identified as serum alpha1-acid glycoprotein was isolated to study its concentration and the dependency of the ester on the brief creation of the indophenolate ion.

Transient Phase and Its Cause

• The research began with an observation of a transient, or short-lived, process in the hydrolysis (breakdown caused by reaction with water) of indophenyl acetate, which was investigated using a stopped-flow spectrophotometer, an instrument used to monitor fast chemical reactions.
• This transient phase was initially something of a mystery to the researchers, who found that it was not caused by the enzyme horse serum cholinesterase, which was the assumed active progressive ingredient in the preparation being used.

Identification of the Active Component

• Upon further investigation, it was discovered that a major component of the preparation, other than the cholinesterase enzyme, was responsible for the transient process observed.
• This surprising discovery led to isolation of the non-cholinesterase component so as to study it in more detail. Ascertaining the nature of this component was important in understanding the process at hand and possibly could lead to improvements or modifications in the preparation.

Subsequent Analyses and Tentative Identification

• The subsequent examinations involved determining the dependence of both the ester (indophenyl acetate) and the non-cholinesterase component’s concentration on the transient creation of the indophenolate ion. This ion is the negatively charged molecule that results from the reaction.
• The careful studies of the isolated component have led to the provisional identification of this active component as serum alpha1-acid glycoprotein. Glycoproteins are proteins that have carbohydrates attached to them and are often involved in the body’s immune response.
• However, this identification is tentative, implying that more research needs to be done for conclusive identification and understanding.