Changes in conformational and functional properties of milk proteins by disulfide reduction and mutation

摘要

To study the superreductivity of a surface disulfide between Cys 6 and 120 in #alpha#-lactalbumin (LA) in contrast to the normal reactivity of the corresponding disulfide in homologous lysozyme (LZ), its energy was estimated by an ab initio calculation with the structural data, and handness and geometrical properties of the disulfide in LA were found to be different from those in LZ, except for the recombinant (r) bovine LA (BLA). The reductivity of the disulfide in r-BLA was then measured and found to be also abnormal. The melting behaviors of the tertiary structure in the (3SS-) derivatives lacking the disulfide of authentic and r-BLAs showed the remaining distortion on the disulfide in both BLAs. Moreover, the disulfide in its mutant L119G was found to be distorted. The lactose synthesis of r-BLA, 3SS-BLA and L119G were compared with that of authentic BLA, and the role of the local conformation near the disulfide for lactose synthesis was discussed.