Journal article
Rice endosperm-specific plastidial α-glucan phosphorylase is important for synthesis of short-chain malto-oligosaccharides
Archives of biochemistry and biophysics, Vol.495(1), pp.82-92
2010
Handle:
https://hdl.handle.net/2376/115764
PMID: 20045390
Abstract
Previous genetic studies have indicated that the type L α-glucan phosphorylase (Pho1) has an essential role during the initiation process of starch biosynthesis during rice seed development. To gain insight into its role in starch metabolism, we characterized the enzymatic properties of the Pho1 recombinant form. Pho1 has significantly higher catalytic efficiency toward both linear and branched α-glucans in the synthesis direction than in the degradation direction with equilibrium constants for the various substrates ranging from 13 to 45. Pho1 activity is strongly inhibited by its own reaction product (Pi) in the synthesis reaction (
K
i
=
0.69
mM) when amylopectin is the primer substrate, but this inhibition is less pronounced (
K
i
=
14.2
mM) when short α-glucan chains are used as primers. Interestingly, even in the presence of Pi alone, Pho1 not only degrades maltohexaose but also extends them to synthesize longer MOSs. Production of a broad spectrum of MOSs (G4–G19) was stimulated by both Pi and Glc1P in an additive fashion. Thus, even under physiological conditions of high Pi/Glc1P, Pho1 extends the chain length of short MOSs which can then be used as subsequent primer by starch synthase activities. As ADP-glucose strongly inhibits Pho1activity, Pho1 likely operates only during the initial stage and not during maturation phase of starch synthesis.
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Details
- Title
- Rice endosperm-specific plastidial α-glucan phosphorylase is important for synthesis of short-chain malto-oligosaccharides
- Creators
- Seon-Kap Hwang - Institute of Biological Chemistry, Washington State University, Pullman, WA99164-6340, USAAiko Nishi - Plant Genetic Resources, Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, JapanHikaru Satoh - Plant Genetic Resources, Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, JapanThomas W Okita - Institute of Biological Chemistry, Washington State University, Pullman, WA99164-6340, USA
- Publication Details
- Archives of biochemistry and biophysics, Vol.495(1), pp.82-92
- Academic Unit
- Biological Chemistry, Institute of
- Publisher
- Elsevier Inc
- Identifiers
- 99900547867701842
- Language
- English
- Resource Type
- Journal article