Pascual R, Burgos F J, Salva M, Soriano F, Mendez E, Aviles F X
Departament de Bioquímica i Biologia Molecular, Facultat de Ciències, Universitat Autònoma de Barcelona, Spain.
Eur J Biochem. 1989 Feb 15;179(3):609-16. doi: 10.1111/j.1432-1033.1989.tb14590.x.
Three different procarboxypeptidases A and two different procarboxypeptidases B have been isolated for the first time, in a pure and native state, from human pancreatic extracts. These proteins were purified in one or two quick steps by anion-exchange HPLC. All these forms have been biochemically characterized. Two of the procarboxypeptidases A, the A1 and A2 forms, are obtained in a monomeric state while the other, the A3 form, is obtained as a binary complex of a procarboxypeptidase A with a proproteinase E. This complex is stable in aqueous buffers at various ionic strengths and develops carboxypeptidase A and proteinase E activities in the presence of trypsin. The A1 and A2 forms show clear differences in electrophoretic mobility in SDS/polyacrylamide gels, isoelectric point, proteolytic activation process with trypsin and susceptibility to thermal denaturation. In contrast, these properties are similar in the A1 and A3 (binary complex) forms. On the other hand, with respect to the properties listed above, the B1 and B2 forms differ from each other mainly in isoelectric point. An overall comparison of the above properties reveals the unusual character of the A2 form, midway between the other A and B forms. N-terminal extended sequence analysis carried out on these proenzymes confirm that they constitute different isologous forms.
首次从人胰腺提取物中以纯的天然状态分离出三种不同的羧肽酶原A和两种不同的羧肽酶原B。这些蛋白质通过阴离子交换高效液相色谱法在一两个快速步骤中得以纯化。所有这些形式均已进行了生化特性鉴定。其中两种羧肽酶原A，即A1和A2形式，以单体状态获得，而另一种，即A3形式，则是作为羧肽酶原A与前蛋白酶E的二元复合物获得。该复合物在不同离子强度的水性缓冲液中稳定，并在胰蛋白酶存在下发挥羧肽酶A和蛋白酶E的活性。A1和A2形式在SDS/聚丙烯酰胺凝胶中的电泳迁移率、等电点、胰蛋白酶的蛋白水解激活过程以及对热变性的敏感性方面存在明显差异。相比之下，A1和A3（二元复合物）形式的这些特性相似。另一方面，就上述特性而言，B1和B2形式主要在等电点上彼此不同。对上述特性的总体比较揭示了A2形式的独特性质，它介于其他A和B形式之间。对这些酶原进行的N端延伸序列分析证实它们构成不同的异源形式。
