Esterase activity of zinc neutral proteases

Area of Science:

• Biochemistry
• Enzymology
• Microbial Proteases

Background:

• Bacterial neutral endopeptidases are zinc-dependent metalloenzymes.
• Their catalytic mechanisms and substrate specificities are well-studied for peptide hydrolysis.

Purpose of the Study:

• To investigate the esterase activity of bacterial zinc neutral endopeptidases.
• To compare the hydrolysis of ester and peptide bonds by these enzymes.

Main Methods:

• Hydrolysis of synthetic depsipeptides and their peptide analogues using purified thermolysin, Bacillus subtilis neutral protease, and Aeromonas proteolytica neutral protease.
• Enzyme kinetics studies, including pH-rate profiles, inhibitor effects, and deuterium isotope effects.
• Metal ion reconstitution experiments on zinc-depleted thermolysin.

Main Results:

• Bacterial zinc neutral endopeptidases exhibit esterase activity, hydrolyzing depsipeptides at slower rates than their peptide counterparts.
• Ester hydrolysis by these enzymes demonstrates specificity for hydrophobic amino acid residues adjacent to the cleavage site, similar to peptide hydrolysis.
• Zinc is essential for the esterase activity of thermolysin; cobalt and zinc ions can restore this activity.
• Kinetic parameters and substrate specificities for ester and peptide hydrolysis by thermolysin are identical.

Conclusions:

• Bacterial zinc neutral endopeptidases possess significant esterase activity.
• The catalytic mechanisms for ester and peptide hydrolysis by these enzymes are conserved.
• Zinc ions play a critical role in mediating both the endopeptidase and esterase functions of these enzymes.