Distribution of carboxypeptidase isoinhibitors in the potato plant.

The total amount of carboxypeptidase inhibitor was estimated in extracts of the leaves, stems, and sprouts of Solanum tuberosum L. cv. Russet Burbank. Although the tuber contained the highest levels on a dry weight basis, inhibitor was also detected in the leaves, sprouts, and upper stems. The relative amounts of each of three carboxypeptidase isoinhibitor families were estimated in several plant tissues by purifying the mixture of isoinhibitors using immobilized carboxypeptidase and then resolving the individual families by polyacrylamide gel electrophoresis. These data demonstrated both that differences in distribution are found in the potato plant and that the three isoinhibitor families described previously (Hass GM, JE Derr, DJ Makus, CA Ryan 1979 Plant Physiol 64: 1022-1028) account for essentially all of the carboxypeptidase inhibitor activity in the tissues studied.