Separation of human pancreatic carboxypeptidase A isoenzymes by high performance liquid chromatography

Human pancreatic carboxypeptidase A, which was isolated from a pool of necrobiotic pancreae, crystallized spontaneously and appeared homogenous in sodium dodecylsulphate polyacrylamide gel electrophoresis. Reversed phase high performance liquid chromatography of the dissolved crystals, however, revealed the presence of two distinct isoenzymes, which were shown by aminoterminal sequence analysis to be only 61% homologous in their 31 amino terminal amino acids. On the other hand, amino terminal sequences of the isoenzymes were found to be 79% and 87% homologous with CAP1 and CPA2 of the rat, respectively. Thus, the presence of two distinct pancreatic carboxypeptidase A isoenzymes could be clearly demonstrated for the first time in human tissue.