Purification and characterization of chymotrypsin inhibitors from marine turtle egg white.
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Date
1984-06
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Abstract
The egg white of marine turtle (Caretta caretta Linn.) contains two chymotrypsin
inhibitors and one trypsin inhibitor. The two chymotrypsin inhibitors were purified to
homogeneity, as judged by ion-exchange chromatography, Polyacrylamide gel and sodium
dodecyl sulphate-gel electrophoresis, isoelectric focusing, immunochemical tests and sedimenttation
in the ultracentrifuge. Their sedimentation coefficient values were independent of
protein concentration. Their amino acid composition was similar, and contained seven
disulphide bonds, and methionine and carbohydrate moiety were absent. Each inhibitor
consisted of a single polypeptide chain of 117 amino acids. The average molecular weight of
each inhibitor, calculated from sedimentation and diffusion coefficient values, amino acid
composition and sodium dodecyl sulphate-gel electrophoresis was 13000. Both the inhibitors
were stable over the pH range of 2–11. They inhibited α-chymotrypsin by forming enzymeinhibitor
complexes at a molar ratio of unity. The dissociation constant of each complex was
1·06 × 10–10
M. Both the inhibitors were indistinguishable in their physical, chemical and
inhibitory properties except for their isoelectric points which were pH 5·23 for inhibitor A and
pH 6·0 for inhibitor B. Chemical modification of all amino groups with trinitrobenzene
sulphonate had no effect on their inhibitory activity.
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Keywords
Protease inhibitor, chymotrypsin, turtle egg white
Citation
Guha M K, Sinha N K. Purification and characterization of chymotrypsin inhibitors from marine turtle egg white. Journal of Biosciences. 1984 June; 6(2): 155-163.