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The interaction of papain with polycations.
C I Mekras1, J B Lawton, R J Washington
1Chemistry Department (I), Imperial College of Science and Technology, University of London, South Kensington, UK.
The Journal of Pharmacy and Pharmacology
|January 1, 1989
Summary
Papain enzyme activity is modulated by polycations like protamine. At low concentrations, these polycations inhibit papain, but at higher concentrations, they can act as weak catalysts, influencing enzyme kinetics.
Area of Science:
- Biochemistry
- Enzymology
- Protein interactions
Background:
- Papain is a cysteine protease with significant biological and industrial applications.
- Polycations are known to interact with proteins, potentially altering their structure and function.
- Understanding these interactions is crucial for controlling papain's enzymatic activity.
Purpose of the Study:
- To investigate the interaction between the enzyme papain and various polycations (protamine, polybrene, poly(L-lysine), spermine, spermidine) and a neutral polymer (polyvinylpyrrolidone, PVP).
- To elucidate the dual role of these compounds as inhibitors and potential catalysts for papain.
- To characterize the binding interaction between papain and dansyl protamine (DNSP) using biophysical techniques.
Main Methods:
- Enzyme inhibition assays were performed to assess papain activity in the presence of different polycations and PVP at varying concentrations.
- Proteolytic activity assays using haemoglobin as a substrate were conducted to evaluate the catalytic potential of polycations.
- Fluorescence polarization technique was employed to study the interaction and complex formation between papain and dansyl protamine (DNSP).
- Critical electrolyte concentration determination was used to quantify the strength of the DNSP-papain binding.
Main Results:
- Polycations and PVP exhibited inhibitory effects on papain at low concentrations.
- At higher concentrations, these compounds showed a decrease in inhibition and, in some cases, acted as weak proteolytic catalysts.
- The catalytic effectiveness ranking was determined as protamine > polybrene > poly(L-lysine) > PVP > spermidine > spermine.
- Fluorescence polarization revealed a strong interaction between papain and DNSP, with a critical electrolyte concentration of 0.2 M NaNO3.
- The stoichiometry of the DNSP-papain complex was found to be 63:1 (DNSP:papain).
Conclusions:
- The observed anomalous inhibition of papain by polycations can be attributed to their weak catalytic activity at higher concentrations.
- Papain exhibits strong binding interactions with polycations, as exemplified by the DNSP-papain complex.
- These findings provide insights into the complex modulation of enzyme activity by charged polymers.