Structural Basis for the Substrate Inhibition of Proline Utilization A by Proline
David A Korasick1, Travis A Pemberton2, Benjamin W Arentson3
1Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA. korasickd@missouri.edu.
Molecules (Basel, Switzerland)
|January 4, 2018
Summary
Substrate inhibition in proline utilization A (PutA) enzymes is caused by proline binding to the wrong active site. This structural finding explains how proline blocks its own breakdown by the glutamate-γ-semialdehyde dehydrogenase (GSALDH) site.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Proline utilization A (PutA) is a bifunctional enzyme catalyzing proline oxidation to glutamate.
- Substrate inhibition by proline is a known kinetic feature of PutA enzymes.
- The structural basis for this substrate inhibition has remained unclear.
Purpose of the Study:
- To elucidate the structural mechanism behind proline-mediated substrate inhibition in PutA.
- To investigate the binding interactions of proline within the PutA enzyme complex.
Main Methods:
- Determined the crystal structure of *Bradyrhizobium japonicum* PutA complexed with proline at 2.15 Å resolution.
- Performed kinetic measurements to assess the inhibitory effects of proline on the GSALDH reaction.
Main Results:
- Proline was observed bound in five locations, including the glutamate-γ-semialdehyde (GSAL) binding site of the GSALDH active site.
- Proline's binding pose in the GSAL site mimics that of the natural substrate, GSAL.
- Kinetic data confirmed proline acts as a competitive inhibitor of the PutA GSALDH reaction.
Conclusions:
- Substrate inhibition of the coupled PRODH-GSALDH reaction by proline is caused by proline binding to the GSAL site.
- This binding event competitively inhibits the GSALDH activity, explaining the observed kinetic behavior.
Keywords:
">l-glutamate-γ-semialdehyde dehydrogenaseX-ray crystallographyflavoenzymeproline dehydrogenasesubstrate inhibitionMore Related Videos
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