ADP-glucose pyrophosphorylase (AGPase) catalyzes the first committed step of starch synthesis in plants. The potato tuber enzyme contains a pair of catalytic small subunits (SSs) and a pair of non-catalytic large subunits (LSs). We have previously identified a LS mutant containing a P52L replacement, which rendered the enzyme with down-regulatory properties. To investigate the structure-function relationships between the two subunits with regard to allosteric regulation, putative SS mutants that could reverse the down-regulatory condition of LSP52L were identified by their ability to restore glycogen accumulation in an AGPase-deficient Escherichia coli glgC-strain. Two distinct LS-dependent classes, bona fide SS suppressors dependent on LSP52L but not LSWT and SS up-regulating allosteric mutants, were evident by kinetic analysis. These results indicate that both LS and SS have a regulatory function in controlling allosteric properties through enhancing cooperative subunit interactions. (C) 2007 Elsevier Inc. All rights reserved.

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glycogen accumulation structurefunction p52l replacement lswt large ss downregulatory condition of lsdependent classes bona starch synthesis small cooperative subunit lsp52l allosteric regulation allosteric properties

.Subunit interactions specify the allosteric regulatory properties of the potato tuber ADP-glucose pyrophosphorylase. 362 (2),6.

"Subunit interactions specify the allosteric regulatory properties of the potato tuber ADP-glucose pyrophosphorylase" 362

"Subunit interactions specify the allosteric regulatory properties of the potato tuber ADP-glucose pyrophosphorylase"