Cystatin like thiol proteinase inhibitor from pancreas of Capra hircus: purification and detailed biochemical characterization
2010
Priyadarshini, Medha | Bano, Bilqees
A thiol proteinase inhibitor from Capra hircus (goat) pancreas (PTPI) isolated by ammonium sulphate precipitation (20-80%) and gel filtration chromatography on Sephacryl S-100HR, with 20.4% yield and 500-fold purification, gave molecular mass of 44 kDa determined by its electrophoretic and gel filtration behavior, respectively. The stokes radius, diffusion and sedimentation coefficients of PTPI were 27.3 Ǻ, 7.87 × 10⁻⁷ cm² s⁻¹ and 3.83 s, respectively. It was stable in pH range 3-10 and up to 70°C (critical temperature, E a = 21 kJ mol⁻¹). Kinetic analysis revealed reversible and competitive mode of inhibition with PTPI showing the highest inhibitory efficiency against papain (K i = 5.88 nM). The partial amino acid sequence analysis showed that it shared good homology with bovine parotid and skin cystatin C. PTPI possessed 17.18% α helical content assessed by CD spectroscopy. The hydropathy plot of first 24 residues suggested that most amino acids of this stretch might be in the hydrophobic core of the protein.
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