2002 Fiscal Year Final Research Report Summary
Biosynthesis of pectin, a plant cell wall polysaccharide
| Project/Area Number |
12640627
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
植物生理
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| Research Institution | Saitama University |
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Principal Investigator |
TSUMURAYA Yoichi Saitama University, Faculty of Science, Professor, 理学部, 教授 (10142233)
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| Project Period (FY) |
2000 – 2002
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| Keywords | cell wall / pectin / galactoronic acid / galacturonosyltransferase |
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| Research Abstract |
Pectins are plant cell wall polysaccharides consisting mainly of contiguous unbranched (1→4)-linked α-galacturonic acid (GalA) residues, and participate in various physiological functions including regulation of cell strength, wall porocity, and intercellular adhesion and communication. A membrane preparation of 7-d-old seedlings from azuki bean (Vigna angularis) contained galacturonosyltransferase (GTase) capable of transferring [^<14>C] GalA from UDP-[^<14>C]GalA into polygalacturonic acid (polyGalA) as an exogenous acceptor. The enzyme was maximally active at pH 6.8-7.5 and 25-35℃ in the presence of 5 mM Mn^<2÷> and 0.5% (w/v) TritonX-100. Acid-soluble low-M_r (average M_r 10,000) polyGalA was a more efficient acceptor substrate than acid-insoluble polymer (M_r 70,000). The apparent Michaelis constants for UDP-GalA and low-M_r polyGalA were 0.11 mM and 0.02 mg/ml, respectively. Various pectins with different degrees of methyl-esterification (DE) were poor acceptors, and the enzyme activity tended to decrease with decreasing DE of the pectins. The transfer products from incubation of the enzyme with UDP-[^<14>C]GalA and the low-M_r polyGalA yielded [^<14>C]GalA_2 as the major product upon digestion with an endopolygalacturonase, confirming the incorporation of GalA into polyGalA through contiguous α-1,4-linkages.
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Research Products
(2 results)
