File(s) under permanent embargo
Catalytically-inactive β-amylase BAM4 required for starch breakdown in Arabidopsis leaves is a starch-binding-protein
journal contribution
posted on 2023-05-18, 11:17 authored by Li, J, Francisco, P, Zhou, W, Edner, C, Steup, M, Ritte, G, Bond, CS, Steven SmithSteven SmithOf the four chloroplast β-amylase (BAM) proteins identified in Arabidopsis, BAM3 and BAM4 were previously shown to play the major roles in leaf starch breakdown, although BAM4 apparently lacks key active site residues and β-amylase activity. Here we tested multiple BAM4 proteins with different N-terminal sequences with a range of glucan substrates and assay methods, but detected no α-1,4-glucan hydrolase activity. BAM4 did not affect BAM1, BAM2 or BAM3 activity even when added in 10-fold excess, nor the BAM3-catalysed release of maltose from isolated starch granules in the presence of glucan water dikinase. However, BAM4 binds to amylopectin and to amylose–Sepharose whereas BAM2 has very low β-amylase activity and poor glucan binding. The low activity of BAM2 may be explained by poor glucan binding but absence of BAM4 activity is not. These results suggest that BAM4 facilitates starch breakdown by a mechanism involving direct interaction with starch or other α-1,4-glucan.
History
Publication title
Archives of Biochemistry and BiophysicsVolume
489Issue
1-2Pagination
92-98ISSN
0003-9861Department/School
School of Natural SciencesPublisher
Academic Press Inc Elsevier SciencePlace of publication
525 B St, Ste 1900, San Diego, USA, Ca, 92101-4495Rights statement
©? 2009 Elsevier Inc. All rights reserved.Repository Status
- Restricted