Substrate specificity of carboxypeptidase from Watermelon.

Area of Science:

• Biochemistry
• Enzymology
• Proteomics

Background:

• Carboxypeptidases are crucial enzymes involved in protein and peptide processing.
• Understanding enzyme substrate specificity is key to elucidating their biological roles and potential applications.
• Watermelon carboxypeptidase (F-II) is a less-studied enzyme with potential biochemical significance.

Purpose of the Study:

• To kinetically characterize the substrate specificity of watermelon carboxypeptidase (F-II).
• To investigate the enzyme's activity towards various synthetic peptides and esters.
• To determine the catalytic site characteristics for peptidase and esterase activities.

Main Methods:

• Kinetic analysis of watermelon carboxypeptidase (F-II) with synthetic dipeptides and esters.
• Enzyme inhibition studies using diisopropyl flurophosphate and specific peptide diastereomers.
• Determination of optimal pH for amidase activity.

Main Results:

• Watermelon carboxypeptidase (F-II) exhibits broad substrate specificity, with rapid hydrolysis of peptides containing hydrophobic amino acids.
• Hydrolysis rates increase with hydrophobic residues at the C-terminal, second, and third positions.
• Peptides with glycine or proline are hydrolyzed slowly; peptidase and esterase activities share a catalytic site but not necessarily the same binding site.

Conclusions:

• Watermelon carboxypeptidase (F-II) demonstrates significant substrate preference for hydrophobic amino acid-containing peptides.
• The enzyme possesses both peptidase and esterase activities, catalyzed by a common active site.
• Amidase activity is observed, with optimal function at pH 7.0.