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Penicillopepsin: 2.8 A structure, active site conformation and mechanistic implications
Advances in Experimental Medicine and Biology
|January 1, 1977
Summary
The crystal structure of penicillopepsin, an acid protease, reveals its active site and catalytic mechanism. This study details the molecule's beta-sheet core and aspartic acid residues involved in substrate hydrolysis.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Penicillopepsin is an extracellular acid protease from Penicillium janthinellum.
- Understanding protease structure and function is crucial in biochemistry and drug development.
Purpose of the Study:
- To determine the crystal structure of penicillopepsin at 2.8 A resolution.
- To elucidate the active site and catalytic mechanism of this acid protease.
Main Methods:
- Multiple isomorphous replacement (MIR) method was used for structure determination.
- X-ray crystallography was employed to resolve the protein structure.
- Electron density maps were computed using native structure factor amplitudes and MIR phases.
Main Results:
- The penicillopepsin molecule is nonspherical, featuring an 18-stranded beta-sheet core around the active site.
- The active site, identified by bound EPNP molecules, involves Asp-32 and Asp-215 in close proximity.
- Hydrogen bonding interactions were observed between Asp-32, Ser-35, and the Thr-216/Gly-217 peptide bond.
Conclusions:
- The determined structure provides insights into the catalytic mechanism of acid proteases, similar to carboxypeptidase A.
- A proposed mechanism involves a shared proton between Asp-32 and Asp-215, water activation, and substrate hydrolysis.
- Tyr-75's phenolic hydroxyl group is proposed to donate a proton to the substrate's scissile bond amide nitrogen.