Hwangbo S, Azuma N, Kurisaki J, Kanno C
Department of Applied Biochemistry, College of Agriculture, Utsunomiya University, Japan.
Biosci Biotechnol Biochem. 1997 Sep;61(9):1568-74. doi: 10.1271/bbb.61.1568.
A monoclonal antibody to the PAS-4 glycoprotein (78 kDa) of the bovine milk fat globule membrane (MFGM) specifically recognized PAS-4, and was named KAS4. A component recognized by KAS4 was found in whey protein, this being a glycoprotein of 88 kDa by SDS-PAGE and named WGP-88. WGP-88 was purified and characterized in comparison with PAS-4. WGP-88 had apparent pI values of 6.45 and 6.39, while those of PAS-4 were 7.39 and 7.35. Neuraminidase digestion shifted the pI values of WGP-88 to 6.57 and of PAS-4 to 7.52. WGP-88 was rich in polar amino residues (44.9 mol%), while PAS-4 was abundant in nonpolar amino acid residues (48.7 mol%). WGP-88 contained 17.1% of carbohydrate and PAS-4 had 7.2%. The results of reductive hydrolysis, N-glycanase digestion, and a lectin blot analysis suggested that N- and O-linked sugar chains were contained in both glycoproteins. WGP-88 and PAS-4 had a different N-terminal amino acid sequence. WGP-88 and PAS-4 respectively inhibited competitively the binding of KAS4 to PAS-4 and WGP-88. Our studies revealed WGP-88 recognized by KAS4 mAb to be a novel whey protein and to have different biochemical properties from those of PAS-4.
一种针对牛乳脂肪球膜（MFGM）的PAS-4糖蛋白（78 kDa）的单克隆抗体特异性识别PAS-4，并被命名为KAS4。在乳清蛋白中发现了一种被KAS4识别的成分，通过SDS-PAGE分析其为一种88 kDa的糖蛋白，命名为WGP-88。对WGP-88进行了纯化，并与PAS-4进行了特性比较。WGP-88的表观pI值为6.45和6.39，而PAS-4的表观pI值为7.39和7.35。神经氨酸酶消化使WGP-88的pI值变为6.57，PAS-4的pI值变为7.52。WGP-88富含极性氨基酸残基（44.9摩尔%），而PAS-4富含非极性氨基酸残基（48.7摩尔%）。WGP-88含有17.1%的碳水化合物，PAS-4含有7.2%。还原水解、N-糖苷酶消化和凝集素印迹分析结果表明，两种糖蛋白均含有N-连接和O-连接的糖链。WGP-88和PAS-4具有不同的N端氨基酸序列。WGP-88和PAS-4分别竞争性抑制KAS4与PAS-4和WGP-88的结合。我们的研究表明，被KAS4单克隆抗体识别的WGP-88是一种新型乳清蛋白，具有与PAS-4不同的生化特性。
