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Purification and characterization of cystatin from duck egg white
1Department of Pharmaceutical Biochemistry, Medical Academy, Wrocław, Poland.
Abstract:
It is the second peptidase inhibitor, after ovostatin, which showing the same antipapain activity in egg white in different avian species implies differences in amino-acid sequences. Cystatin from duck egg white was purified by carboxymethylpapain affinity chromatography and size-exclusion HPLC. The purified inhibitor which showed partial identity in the immunodiffusion test with chicken egg white cystatin, had an apparent molecular mass of 9.3 kDa as determined by SDS/PAGE. IEF analysis revealed five molecular forms of pI in the range 7.8-8.4. The obtained cystatin was neither glycosylated nor phosphorylated as it is in the case of chicken cystatin. The determined Ki (0.005 +/- 0.001 nM) was similar to that reported for human and chicken cystatin C.