Marked differences between metalloproteases meprin A and B in substrate and peptide bond specificity

Area of Science:

• Biochemistry
• Enzymology
• Protease research

Background:

• Meprin A and B are secreted metalloendopeptidases found on cell surfaces, primarily in the kidney and intestine.
• They exist as oligomers composed of alpha and/or beta subunits, which are evolutionarily related.

Purpose of the Study:

• To identify bioactive peptides and proteins hydrolyzed by mouse meprins.
• To kinetically characterize the hydrolysis activity of meprin A and B.
• To elucidate the substrate specificity differences between meprin alpha and beta subunits.

Main Methods:

• Hydrolysis assays using peptide libraries and naturally occurring peptides.
• Kinetic characterization of meprin hydrolysis.
• Homology modeling of meprin alpha and beta protease domains based on astacin structure.

Main Results:

• Gastrin-releasing peptide fragment 14-27 and gastrin 17 were identified as optimal substrates for meprin A and B, respectively.
• Meprin beta subunit demonstrated a preference for acidic amino acids at P1 and P1' sites.
• Meprin alpha subunit favored small or hydrophobic residues at P1 and P1' sites, with proline preferred at P2'.
• Homology models revealed active site differences correlating with distinct substrate specificities.

Conclusions:

• Despite sharing high amino acid identity and localization, meprin alpha and beta subunits exhibit significantly different substrate and peptide bond specificities.
• These distinct specificities suggest divergent functional roles for the meprin subunits.
• Active site structural variations explain the observed differences in substrate preference between meprin alpha and beta.