Characterization of a cDNA encoding a type I starch branching enzyme produced in developing wheat (Triticum aestivum L.)kernels

This report describes the characterization of a 2.8 kb full-length cDNA, coding for a starch branching enzyme I, denoted SBEI-2, which is produced in the wheat endosperm. The deduced SBEI-2 sequence predicted an 832 residue long precursor protein with a 61 amino acid long transit peptide at the amino terminus. A molecular mass of 87.4 kDa was calculated for the mature form of SBEI-2, which showed high sequence similarity (≫82 percnt;) to SBEI characterized from rice and maize. All conserved amino acids at the catalytic site of amylolytic enzymes were preserved on SBEI-2, and the protein was active as a branching enzyme when produced in Escherichia coli. Analysis of SBEI gene expression during wheat kernel development showed that accumulation of 2.8 kb SBEI gene transcripts was highest around 15 days after anthesis.