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Subunit Structure of Spinach Leaf ADPglucose Pyrophosphorylase
M K Morell1, M Bloom, V Knowles
1Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824-1319.
Plant Physiology
|September 1, 1987
Summary
Researchers purified spinach ADPglucose pyrophosphorylase (AGP) and found it has two distinct subunits. These subunits differ in sequence, structure, and immunological properties, with only one related to AGP from other plants.
Area of Science:
- Biochemistry
- Plant Molecular Biology
- Enzyme Structure and Function
Background:
- ADPglucose pyrophosphorylase (AGP) is a key enzyme in plant starch biosynthesis.
- Previous studies suggested AGP is composed of multiple subunits, but their distinct roles and properties were unclear.
Purpose of the Study:
- To develop an improved purification method for spinach AGP for structural studies.
- To characterize the subunits of spinach AGP and investigate their relationship to AGP from other species.
Main Methods:
- Developed an improved purification protocol yielding 20-30 mg of pure spinach AGP.
- Utilized SDS-PAGE, Western blotting, anion-exchange chromatography with urea, N-terminal sequencing, and tryptic peptide mapping.
- Performed immunological comparisons using Western blot analysis.
Main Results:
- The purified spinach AGP consists of two subunits migrating at 51 and 54 kDa.
- These subunits exhibit distinct N-terminal amino acid sequences and tryptic peptide maps.
- Western blot analysis revealed antigenic differences between the subunits; the 51 kDa subunit showed immunological similarity to AGP from maize and potato, but the 54 kDa subunit did not.
Conclusions:
- Spinach ADPglucose pyrophosphorylase is composed of two distinct subunits with differing biochemical and immunological properties.
- The 51 kDa subunit is evolutionarily conserved and shares immunological similarity with AGP from other plant sources.
- This study provides a foundation for further structural and functional investigations of spinach AGP.
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