3 ISOFORMS OF STARCH SYNTHASE AND 2 ISOFORMS OF BRANCHING ENZYME ARE PRESENT IN POTATO-TUBER STARCH

Proteins were extracted from tuber starch of a normal and a transgenic potato line and separated by SDS gel electrophoresis. Granule-bound s tarch synthase I (GBSS I) was absent in the latter potato. In-gel dige stion of specific protein bands, isolation of peptides by reversed pha se chromatography and finally sequencing, showed that three isoforms o f starch synthase and two isoforms of branching enzyme (SEE) were pres ent in the starch. A cDNA fragment for SEE II was isolated.