Proteolysis of bovine alpha -lactalbumin by thermolysin during thermal denaturation.

摘要

Thermolysin was used to hydrolyze bovine alpha -lactalbumin at 25 and 70 degrees C under non-reducing conditions. The breakdown products were identified by mass spectrometry. At 25 degrees C, the low proportion of alpha -lactalbumin in an unfolded state in equilibrium with the native state underwent limited hydrolysis leading to the production of peptides, that were no longer degraded (final peptides). At 70 degrees C, the protein was in a molten globule-like state according to circular dichroism and complete cleavage of the protein was achieved. At 70 degrees C, the protein was first quickly cleaved, then unfolded, leading to the release of intermediate peptides, from which final peptides were eventually produced. The amino-terminal 1-58 and carboxy-terminal 95-123 regions were readily cleaved, whereas the central region including the calcium-binding domain was more resistant. Some peptides were produced at 70 degrees C, but not at 25 degrees C. The choice of accurate experimental conditions may be of importance for the preparation of functional peptides..