Enzymic degradation of allantoate in developing soybeans
R G Winkler1, J C Polacco, D G Blevins
1Biochemistry Department, M121 Medical Sciences Building, University of Missouri, Columbia, Missouri 65212.
Plant Physiology
|November 1, 1985
Summary
Soybean extracts contain a manganese-dependent enzyme that breaks down allantoate into carbon dioxide and ammonia. This enzyme is primarily located in seed coats, suggesting a role in nitrogen metabolism before it reaches the embryo.
Area of Science:
- Plant Biochemistry
- Nitrogen Metabolism
- Enzymology
Background:
- Allantoate is a key nitrogenous compound in legumes.
- Understanding allantoate breakdown is crucial for plant nitrogen utilization.
Purpose of the Study:
- To detect and characterize the enzymic breakdown of allantoate in soybeans.
- To elucidate the products and kinetics of this allantoate-degrading activity.
Main Methods:
- Enzymatic assays using crude and partially purified soybean extracts.
- High-performance liquid chromatography (HPLC) for product identification.
- Kinetic analysis (K(m)) and inhibitor studies.
Main Results:
- A Mn(2+)-dependent allantoate breakdown pathway was identified.
- Key products include CO(2), NH(3), glyoxylate, and urea.
- The enzyme exhibits a K(m) of 1.0 mM for allantoate and is inhibited by EDTA, borate, and acetohydroxamate.
- Activity is significantly higher in seed coats than embryos.
Conclusions:
- Soybeans possess a urease-independent pathway for allantoate degradation.
- This pathway likely plays a role in nitrogen mobilization within the seed coat.
- The identified enzyme is distinct from allantoate amidinohydrolase.
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