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Comparative physicochemical studies of human α-lactalbumin and human lysozyme

par Barel, André ;Prieels, Jean-Paul ;Maes, Emmanuel;Looze, Yvan ;Leonis, José
Référence BBA - Protein Structure, 257, 2, page (288-296)
Publication Publié, 1972-02

Article révisé par les pairs

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Résumé :

As a result of the recent disclosure of the striking similarities between the covalent structures of bovine α-lactalbumin and of hen egg-white lysozyme, comparative physicochemical properties of α-lactalbumins and lysozymes of various sources seemed worth investigating. Therefore human milk α-lactalbumin and human milk or urinary lysozyme were purified. Their physical properties were examined in order to study the extent of similarity of the three-dimensional structure when considering the two proteins from the same species. Diffusion and sedimentation experiments showed that the hydrodynamic shape and the molecular weight of human α-lactalbumin and lysozyme were strikingly comparable. Concerning the secondary structure, it was observed by optical rotatory dispersion and circular dichroism that human lysozyme displays slightly more helix than human α-lactalbumin. Furthermore, when considering thermal denaturation, the transition temperatures and changes in enthalpy or entropy are all markedly lower for human α-lactalbumin than for lysozyme. These findings have been discussed in relation to the physicochemical properties of bovine α-lactalbumin and egg-white lysozyme. © 1972.