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Inhibition of pepsin by polyions and c.d. studies.
1Chemistry Department, Imperial College of Science, Technology and Medicine, University of London, UK.
International Journal of Biological Macromolecules
|August 1, 1989
Summary
Polyions like poly(vinyl sulphate) (PVS), poly(vinyl pyrrolidone) (PVP), and protamine inhibit pepsin at low concentrations. Their effectiveness as pepsin inhibitors and proteolytic catalysts varies, with polybrene being the most effective.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Pepsin (EC 3.4.23.1) is a key digestive enzyme.
- The interaction of polyions with enzymes can modulate their activity.
Purpose of the Study:
- To investigate the effects of poly(vinyl sulphate) (PVS), poly(vinyl pyrrolidone) (PVP), and protamine on pepsin activity.
- To assess the catalytic effectiveness of various polyions with pepsin.
- To determine the binding interactions between polyions and pepsin.
Main Methods:
- Enzyme inhibition assays using hemoglobin and azocasein as substrates.
- Determination of enzyme purity via SDS-PAGE, phosphorus, and nitrogen content analysis.
- Circular dichroism (c.d.) spectroscopy to study polyion-pepsin binding.
Main Results:
- PVS, PVP, and protamine inhibited pepsin at low concentrations; inhibition decreased at high polyion concentrations (except for PVS).
- Polyions exhibited varying proteolytic catalytic effectiveness with pepsin, with polybrene > poly(L-lysine) (PLL) > spermine > spermidine > protamine > PVP.
- High salt concentrations reduced pepsin's substrate hydrolysis.
- Circular dichroism indicated strong binding of polyions to pepsin, with interaction strength: polybrene > protamine > PLL > PVP > spermidine > spermine.
Conclusions:
- Polyions significantly influence pepsin activity, acting as inhibitors and weak catalysts.
- The binding affinity of polyions to pepsin varies, impacting enzyme function.
- Polyion-enzyme interactions are complex and concentration-dependent.