A novel form of pectinesterase in tomato.

The pectinesterases in tomato pericarp were fractionated by cation exchange into four forms (A-D). Form A was the most abundant and C the second most abundant. Forms A-C were further purified by gel filtration, and antibodies were raised against A and C. Comparison of the different forms by dot blots and Western blots showed that although all three forms shared common immunological characteristics, there were also differences in their behaviour, indicative of structural differences. Form A had an N-terminal sequence identical to that published previously for the major pectinesterase in tomato fruit. In contrast, form C had a completely novel N-terminal sequence. Form A was absent from hypocotyls and roots. Forms B and C were present in comparable amounts in hypocotyls, while from C predominated in roots.