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Studies on the Interaction of Papain with Human Placental Cystatin by Uv, Fluorescence and Cd Spectroscopy

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The interaction of activated papain with low molecular weight cystatin (Mr 12500) purified from human placenta has been studied. Analysis of inhibition of caesinolytic activity of papain by cystatin showed stoichiometry of 1:1. Kinetic studies gave an inhibition constant (Ki) value of 5.5 x 10 -8 M and association rate constant (K+1) value of 3.4 x 10 4 (M-1 s-1). All spectroscopic studies showed conformational changes in both papain and cystatin on formation of complex. The data suggest perturbation of environment of aromatic residues and change of their native structure and conformation thereby shedding light on the behaviour of cystatins, especially interaction of placental cystatin with thiol protease inhibitors.

Keywords: cystatin; far uv-cd spectroscopy; fluorescence emission; human placenta; papain; uvabsorption

Document Type: Review Article


Affiliations: Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, India.

Publication date: December 1, 2004

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  • Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.

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