Cloning of ADP-glucose pyrophosphorylase cDNAs from Chinese cabbage (Brassica campestris L. spp. pekinensis)

Abstract

ADP-glucose pyrophosphorylase (AGPase, EC2.7.7.27) catalyzes the key regulatory step in starch biosynthesis. cDNA clones encoding two different AGPase polypeptides denoted small subunit (BCAGPS) and large subunit (BCAGPL) were isolated from Chinese cabbage (Brassica campestris L. spp. pekinensis) cDNA library. The BCAGPS cDNA has an 1557 base pairs open reading frame which encodes a protein of deduced 519 amino acids. The deduced amino acid sequence exhibits a high degree of homology with small subunit AGPase proteins from potato (with 90% of identical amino acid) and pea (with 89% of identical amino acid). The BCAGPL cDNA has an 1662 base pairs open reading frame which encodes a protein of deduced 554 amino acids. The deduced amino acid sequence exhibits a homology with large subunit AGPase proteins from potato (with 72% of identical amino acid) and pea (with 66% of identical amino acid). It is also appeared that the small subunit is more conserved among the different plants and the large subunit more divergent. Deduced amino acid comparisons with other plants revealed conserved regions important for substrate binding and allosteric regulation of AGPase enzyme.