Discipline: Chemistry and Chemical Sciences
Subcategory: Cancer Research
Brittini Roye - University of the District of Columbia
Co-Author(s): Xueqing Song, University of the District of Columbia
The cysteine proteases are a large group of enzymes that play roles in a broad range of biological processes. Disturbance of the natural equilibrium of enzymatic activity of the cysteine proteases, responsible for protein degradation, may lead to a variety of pathological conditions, including Alzheimer’s, stroke and cancer. Inhibitors can restore the normal balance through regulation of these enzymes and therefore present an opportunity for drug development. The main objective of this project is to investigate whether triorganotin can inhibit enzymatic activity of thiol-dependent cysteine proteases. The research is based on the hypothesis that a triorganotin complex has strong interaction with thiol group and could inhibit a cysteine protease by ligand exchange with the thiol of the active site cysteine. In this experiment, commercial available triphenyltin acetate was choosed as the inhibitor of Papain, a cysteine protease used in this project. The enzymatic activities of both pure and inhibited papain solutions were recorded based on the amount of tyrosine released in digesting reaction of Casein. The Folin and Ciocalteus Phenol, or Folin’s reagent was used to react with free tyrosine to produce a blue colored chromophore, which was quantifiable and measured as an absorbance value on the spectrophotometer. High absorbance on the spectrophotometer indicated the stronger the activity of the protease. Absorbance values generated by the activity of the protease were then compared to a standard curve, which was generated by reacting known quantities of tyrosine with the F-C reagent to correlate changes in absorbance with the amount of tyrosine. A standard curve has been generated between the enzymatic activity and the absorbance under 660 nm. From the standard curve the activities of tested pure and inhibited Papain solutions were determined. Preliminary data showed that the enzymatic activity of Papain was inhibited by triphenyltin acetate with the concentration in a range of .5 to 2 ppm in acetone. However, the inhibition of triphenyltin acetate showed no significant difference when the tin concentration was changed in acetone. This could be due to the limited amount of thiol sites in papain, as in commercial papain the thiol group exists in the form of S-S bridge, and an activation of the thiol sites should be done before the essay to readily reacts with tin complxes. When dimethyl sulfoxide was used as the solvent, no inhibition was observed for triphenyltin actetate. This indicated that triphenyltin acetate can be used as a potential cysteine protease inhibitor if it has appropriate solubility in water. Future studies of this project will focus on triorganotin complexes with high water solubility. Activation of the thiol groups in Papin should also be considered to improve the inhibitory activity of tin complexes.
Funder Acknowledgement(s): This research was supported by NSF/HRD1531014.
Faculty Advisor: Xueqing Song, email@example.com
Role: This research was a collective effort between myself and Dr. Xueqing Song.