Direct appraisal of the potato tuber ADP-glucose pyrophosphorylase large subunit in enzyme function by study of a novel mutant form

Seon-Kap Hwang; Yasuko Nagai; Dongwook Kim; Thomas W Okita

doi:10.1074/jbc.M707447200

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Direct appraisal of the potato tuber ADP-glucose pyrophosphorylase large subunit in enzyme function by study of a novel mutant form

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Direct appraisal of the potato tuber ADP-glucose pyrophosphorylase large subunit in enzyme function by study of a novel mutant form

Seon-Kap Hwang, Yasuko Nagai, Dongwook Kim and Thomas W Okita

The Journal of biological chemistry, Vol.283(11), pp.6640-6647

03/14/2008

DOI: https://doi.org/10.1074/jbc.M707447200

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https://hdl.handle.net/2376/105634

PMID: 18199755

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Abstract

Glucose-1-Phosphate Adenylyltransferase - physiology

Protein Structure, Tertiary

Mutagenesis, Site-Directed

Models, Molecular

Recombinant Proteins - chemistry

Glyceric Acids - chemistry

Structure-Activity Relationship

Dose-Response Relationship, Drug

Solanum tuberosum - enzymology

Glycogen - chemistry

Catalysis

Kinetics

Mutation

Binding Sites

Dimerization

Glucose-1-Phosphate Adenylyltransferase - genetics

The higher plant ADP-glucose pyrophosphorylase is a heterotetramer consisting of two subunit types, which have evolved at different rates from a common ancestral gene. The potato tuber small subunit (SS) displays both catalytic and regulatory properties, whereas the exact role of the large subunit (LS), which contains substrate and effector binding sites, remains unresolved. We identified a mutation, S302N, which increased the solubility of the recombinant potato tuber LS and, in turn, enabling it to form a homotetrameric structure. The LS302N homotetramer possesses very little enzyme activity at a level 100-fold less than that seen for the unactivated SS homotetramer. Unlike the SS enzyme, however, the LS302N homotetramer enzyme is neither activated by the effector 3-phosphoglycerate nor inhibited by P(i). When combined with the catalytically silenced SS, S D143N, however, the LS302N-containing enzyme shows significantly enhanced catalytic activity and restored 3-PGA activation. This unmasking of catalytic and regulatory potential of the LS is conspicuously evident when the activities of the resurrected L(K41R.T51K.S302N) homotetramer are compared with its heterotetrameric form assembled with S D143N. Overall, these results indicate that the LS possesses catalytic and regulatory properties only when assembled with SS and that the net properties of the heterotetrameric enzyme is a product of subunit synergy.

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Title: Direct appraisal of the potato tuber ADP-glucose pyrophosphorylase large subunit in enzyme function by study of a novel mutant form
Creators: Seon-Kap Hwang - Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340, USA
Yasuko Nagai
Dongwook Kim
Thomas W Okita
Publication Details: The Journal of biological chemistry, Vol.283(11), pp.6640-6647
Academic Unit: Biological Chemistry, Institute of
Publisher: United States
Identifiers: 99900546780501842
Language: English
Resource Type: Journal article