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A peptidase activity exhibited by human serum pseudocholinesterase
European Journal of Biochemistry
|January 2, 1987
Summary
Human serum pseudocholinesterase (PsChE) exhibits peptidase activity, confirmed through various purification and characterization techniques. This dual enzymatic function is inhibited by choline esters, suggesting a conformational change affecting a peptidase domain.
Area of Science:
- Biochemistry
- Enzymology
- Protein Chemistry
Background:
- Human serum pseudocholinesterase (PsChE) is a well-characterized enzyme primarily known for its esterase activity.
- The potential peptidase activity of PsChE has been investigated, but its identity and characteristics remain less understood.
Purpose of the Study:
- To identify and characterize the peptidase activity associated with purified human serum pseudocholinesterase (PsChE).
- To elucidate the relationship between PsChE's esterase and peptidase functions.
Main Methods:
- Purification of PsChE using affinity chromatography (procainamide-Sepharose, concanavalin-A--Sepharose).
- Enzyme characterization via gel electrophoresis, gel filtration, and antibody precipitation.
- Assay of peptidase activity using various peptides and inhibition studies with specific PsChE inhibitors and choline esters.
Main Results:
- Peptidase activity was consistently found with purified PsChE, co-eluting and co-migrating with the enzyme.
- The enzyme exhibited a single protein band under non-denaturing and reducing SDS-PAGE conditions (Mr ~90,000).
- Peptidase activity involved the release of C-terminal amino acids, and was not inhibited by typical PsChE esterase or anionic site inhibitors, but was significantly inhibited by choline esters.
Conclusions:
- The peptidase activity is an intrinsic property of human serum pseudocholinesterase.
- Inhibition by choline esters suggests that compounds binding to both anionic and esteratic sites induce conformational changes that impact the peptidase domain.