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Three-dimensional molecular modeling explains why catalytic function for angiotensin-I is different between human and
D Yamamoto1, N Shiota, S Takai
1Medical Computation Center, Osaka Medical College, Japan.
Biochemical and Biophysical Research Communications
|January 24, 1998
Summary
Human chymase (HC) and rat chymase (RMCP-I) exhibit distinct angiotensin (ANG)-I cleavage sites due to electrostatic differences. Molecular dynamics simulations reveal these differences, explaining varied enzyme catalysis at the atomic level.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Angiotensin (ANG)-I is a substrate for chymase, but cleavage sites vary across chymase families.
- Human chymase (HC) cleaves ANG-I at Phe8-His9, producing ANG-II, while rat chymase (RMCP-I) cleaves at Tyr4-Ile5, yielding inactive fragments.
Purpose of the Study:
- To elucidate the atomic-level catalytic differences between HC and RMCP-I in ANG-I hydrolysis.
- To understand the structural basis for the distinct substrate specificities of HC and RMCP-I.
Main Methods:
- Construction of three-dimensional structures for HC and RMCP-I using molecular dynamic simulations.
- Energy refinement of enzyme models.
- Molecular modeling of enzyme-substrate complex structures with ANG-I.
Main Results:
- Energy-refined models revealed significant differences in the electrostatic potential on the solvent surface of HC and RMCP-I.
- Modeling of enzyme-ANG-I complexes indicated that functional differences are linked to electrostatic variations.
- These electrostatic differences are particularly pronounced at the C-terminal substrate-binding site.
Conclusions:
- The distinct catalytic activities of HC and RMCP-I on ANG-I are attributable to differences in their electrostatic surface potentials.
- Structural insights at the atomic level explain the functional divergence in chymase-mediated ANG-I processing.