Chaplin B, Green M L
National Institute for Research in Dairying, Shinfield, Reading RG2 9AT, United Kingdom.
Biotechnol Bioeng. 1982 Dec;24(12):2627-41. doi: 10.1002/bit.260241203.
Soluble conjugates of pepsin and carboxypeptidase A were prepared by covalent linkage of the enzymes to an amino derivative of dextran. By fractionating the dextran derivatives before and after enzyme coupling, three conjugates, with median Stokes radii between 4.0 and 11.7 nm and with a range of 25% of the median, were prepared from each enzyme. The pepsin and carboxypeptidase A conjugates contained about 35% and 3% protein, respectively. Both types had specific activities close to those of the native enzymes and were stable at -20 degrees C. The pH-activity curve was unaffected by linkage of either enzyme to dextran. The stabilities at 30 degrees C of pepsin at pH 6-7 and carboxypeptidase A at pH 3.5-9.0 were increased by linkage to dextran. No significant amount of unbound enzyme was released from either type of conjugate in skim milk. The molecular sizes, deduced from the intrinsic viscosities and the diffusion coefficients of all conjugates, were close enough to the Stokes radii to indicate that the molecules were approximately spherical. Physical measurements also indicated that the molecules were dextranlike and highly hydrated.
通过将胃蛋白酶和羧肽酶A与葡聚糖的氨基衍生物共价连接，制备了它们的可溶性结合物。通过在酶偶联前后对葡聚糖衍生物进行分级分离，从每种酶中制备了三种结合物，其斯托克斯半径中位数在4.0至11.7纳米之间，范围为中位数的25%。胃蛋白酶和羧肽酶A结合物分别含有约35%和3%的蛋白质。两种类型的结合物的比活性都接近天然酶，并且在-20℃下稳定。pH-活性曲线不受任何一种酶与葡聚糖连接的影响。通过与葡聚糖连接，胃蛋白酶在pH 6-7时以及羧肽酶A在pH 3.5-9.0时在30℃的稳定性增加。在脱脂牛奶中，两种类型的结合物均未释放出大量未结合的酶。根据所有结合物的特性粘度和扩散系数推导得出的分子大小，与斯托克斯半径足够接近，表明分子近似球形。物理测量还表明，这些分子类似葡聚糖且高度水合。
