MOLECULAR-CLONING AND CHARACTERIZATION OF STARCH-BRANCHING ENZYME-II FROM POTATO

Full-length cDNA for starch branching enzyme (SBE) II of potato was is olated and sequenced. In potato, similary to most other investigated p lants, the SEE-II isoform differs from SEE-I by having an acidic amino -terminal extension and a shorter carboxyterminus. Two forms of SEE-II , migrating as 98 and 95 kDa proteins in 6% SDS-polyacrylamide gels, w ere associated to tuber starch. The latter form was 16 amino acids sho rter in the amino terminus. Transcript of SEE-II was present in leaf t issue, whereas significant expression was not seen in tubers. On the o ther hand, a significant amount of SEE-I transcript was detected in tu ber tissue but not in leaves.