Biochemical, immunological and kinetic characterization and partial sequence analysis of a thiol proteinase inhibitor from Bubalus bubalis kidney: An attempt targeting kidney disorders

In the present study a thiol proteinase inhibitor was isolated from buffalo kidney making use of ammonium sulphate precipitation and gel filtration chromatography on Sephacryl S-100HR column. Purified inhibitor is homogeneous as it displayed a single band in gel electrophoresis both under reducing and non-reducing environment and is of 65 KDa as revealed by gel filtration and SDS PAGE. Kinetic studies revealed the presence of reversible accompanied with competitive mode of inhibition; showing maximum efficacy against papain (K_i = 2.90 × 10⁻⁴). It was maximally active at pH 8.0 and was stable for a period of 30, 60 and 90 days at 37, 4 and −20 °C respectively. Immunological studies confirmed its purity of epitopes as a single precipitin line is obtained in immunodiffusion. N-terminal analysis revealed that it shared a good homology with mouse kidney cystatin as well as with Human Cys C and Cys E thereby advocating its use as a model for various human oriented studies which targets how the kidney cystatin level varies in accordance with various drugs that are currently being used as a target for variety of diseases.