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Characterization of soybean endopeptidase activity using exogenous and endogenous substrates
1Department of Biochemistry, University of Leeds, Leeds, LS2 9JT United Kingdom.
Plant Physiology
|June 1, 1983
Summary
Soybean seeds contain two main endopeptidase activities: metalloendopeptidases and carboxylendopeptidases. These enzymes degrade specific seed proteins, but not all, revealing distinct substrate specificities.
Area of Science:
- Biochemistry
- Plant Science
- Enzymology
Background:
- Mature soybean seeds (Glycine max) possess enzymatic activity crucial for protein turnover.
- Understanding endopeptidase function is key to seed physiology and development.
Purpose of the Study:
- To characterize the distinct endopeptidase activities present in soybean seeds.
- To identify the substrates and specificities of these enzymes.
Main Methods:
- Enzyme assays using [(125)I]iodoinsulin B chain as an exogenous substrate.
- Analysis of pH optima and inhibition patterns to differentiate enzyme activities.
- Investigation of degradation patterns on endogenous seed proteins.
Main Results:
- Two primary endopeptidase activities were identified: a neutral/alkaline metalloendopeptidase and an acidic carboxylendopeptidase.
- Metalloendopeptidases degraded certain storage protein subunits, but not the beta subunit of conglycinin or other specific polypeptides.
- Carboxylendopeptidases primarily degraded an acid-soluble 30,000 MW polypeptide, while soybean agglutinin was resistant to both activities.
Conclusions:
- Soybean seeds exhibit distinct metallo- and carboxyl-endopeptidase activities with specific substrate preferences.
- These enzymes play a role in limited proteolysis of seed proteins, with certain components like conglycinin and soybean agglutinin showing resistance.
