Year: 2002
Type: dissertation
Abstract: Starch debranching enzymes, which specifically hydrolyse a-1,6glucosidic bonds in glucans containing both a-1,4 and a-1,6 linkages, are classified into two types: isoamylase (EC.3.2.1.68)and limit dextrinase (EC. 3.2.1.41).The starch debranching enzymes are primarily involved in starch degradation during seed germination.Recently, however, starch debranching enzymes, particularly isoamylase, have been implicated in starch biosynthesis in many plant species.In this study, a 2,590-bp isoamylase cDNA, which encoded an 88-kDa isoamylase pre-protein containing the N-terminal transit peptide of 5 kDa, was isolated from a developing wheat kernel cDNA library.The recombinant protein produced in E. coli by expression of the cDNA exhibited isoamylase-type debranching enzyme activity.Accumulation of the 2.6-kb isoamylase transcripts in various tissues of wheat indicated the involvement of isoamylase in both starch synthesis in storage and non-storage organs, and starch degradation during seed germination.In the early stages during wheat kernel development, the presence of a 1.7-kb transcript was observed.The 1.7-kb transcript encoded a 51-kDa truncated isoamylase, whose starch debranching enzyme activity could not be detected in vitro.Southern blot analysis of genomic DNA of hexaploid wheat (Triticum aestivum L. cultivar CDC Teal) showed that isoamylase gene existed as a single copy in the wheat genome.Therefore, the production of various isoamylase transcripts and the involvement of isoamylase during two developmental stages of wheat plant may result from transcriptional i i
Author: Supatcharee Netrphan
Language: English
Subfield: Plant Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W1479866592