Functional changes of [chicken egg] lysozyme by conjugating with carboxymethyl dextran
1994
Hattori, M. (Tokyo Univ. of Agriculture and Technology, Fuchu (Japan). Faculty of Agriculture) | Imamura, S. | Nagasawa, K. | Takahashi, K.
Hen egg lysozyme-carboxymethyl dextran (HEL-CMD) conjugate was prepared by using water-soluble carbodiimide as a model protein-acidic polysaccharide conjugate for improving the protein function. An acid-amide bond between HEL and CMD was confirmed by SDS-PAGE, isoelectric focusing and IR spectra. The molar ratio of CMD to HEL in the conjugate was 1:1. The isoelectric point of the conjugate was 5.5-6.0, which is much lower than that of HEL. Spectroscopic studies suggested that the conformation around the Trp residue had not changed but the alpha-helix content had decreased to about 1/3 that for native HEL. The conjugate maintained about 60% of the enzymatic activity of native HEL at 40-60 degrees C, while it was about 1.4 times as active as native HEL at 4 degrees C and 80 degrees C. The conjugate was more stable to proteolysis than native HEL. The denaturation temperature of the conjugate was about 73 degrees C, which is almost the same as that of native HEL. However, the enthalpy for denaturation of the conjugate was about 1/3 that of native HEL, which corresponds to the decrease in alpha-helix content
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