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Glucan, water dikinase activity stimulates breakdown of starch granules by plastidial β-amylases

Citation

Edner, C and Li, J and Albrecht, T and Mahlow, S and Hejazi, M and Hussain, H and Kaplan, F and Guy, C and Smith, SM and Steup, M and Ritte, G, Glucan, water dikinase activity stimulates breakdown of starch granules by plastidial β-amylases, Plant Physiology, 145, (1) pp. 17-28. ISSN 0032-0889 (2007) [Refereed Article]

Copyright Statement

Copyright 2007 American Society of Plant Biologists

DOI: doi:10.1104/pp.107.104224

Abstract

Glucan phosphorylating enzymes are required for normal mobilization of starch in leaves of Arabidopsis (Arabidopsis thaliana) and potato (Solanum tuberosum), but mechanisms underlying this dependency are unknown. Using two different activity assays, we aimed to identify starch degrading enzymes from Arabidopsis, whose activity is affected by glucan phosphorylation. Breakdown of granular starch by a protein fraction purified from leaf extracts increased approximately 2-fold if the granules were simultaneously phosphorylated by recombinant potato glucan, water dikinase (GWD). Using matrix-assisted laser-desorption ionization mass spectrometry several putative starch-related enzymes were identified in this fraction, among them β-AMYLASE1 (BAM1; At3g23920) and ISOAMYLASE3 (ISA3; At4g09020). Experiments using purified recombinant enzymes showed that BAM1 activity with granules similarly increased under conditions of simultaneous starch phosphorylation. Purified recombinant potato ISA3 (StISA3) did not attack the granular starch significantly with or without glucan phosphorylation. However, starch breakdown by a mixture of BAM1 and StISA3 was 2 times higher than that by BAM1 alone and was further enhanced in the presence of GWD and ATP. Similar to BAM1, maltose release from granular starch by purified recombinant BAM3 (At4g17090), another plastid-localized β-amylase isoform, increased 2- to 3-fold if the granules were simultaneously phosphorylated by GWD. BAM activity in turn strongly stimulated the GWD-catalyzed phosphorylation. The interdependence between the activities of GWD and BAMs offers an explanation for the severe starch excess phenotype of GWD-deficient mutants.

Item Details

Item Type:Refereed Article
Keywords:glucan, water dikinase, beta-amylase, arabidopsis thaliana, starch,
Research Division:Biological Sciences
Research Group:Plant Biology
Research Field:Plant Physiology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Biological Sciences
Author:Smith, SM (Professor Steven Smith)
ID Code:101506
Year Published:2007
Web of Science® Times Cited:105
Deposited By:Plant Science
Deposited On:2015-06-25
Last Modified:2015-09-24
Downloads:0

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