Use of a 49-peptide library for a qualitative and quantitative determination of pseudomonal serralysin specificity

The Pseudomonas aeruginosa serralysin (E.C. 3.4.24.40.), which is a zinc-dependent metalloprotease from the metzincin superfamily, has quite a broad specificity, which has not yet been clearly identified. We have studied it with an original approach, using a 49-peptide library of the type Z-AXXA (amide) (X = A, L, V, F, S, R, E). The library was analyzed by LC-MS before and after enzymatic hydrolysis. A great number of hydrolyzed peptides were screened and the preferential hydrolysis was the X-X peptide bond, even if in some cases, A-X and X-A bond could be hydrolyzed. No amino acids with a ionized side chain could be found in the P1' position. The results obtained suggest that the specificity in the P1' position, where an hydrophobic residue was preferentially found, seems more selective that in the Pn position. The P1 position was not very specific, but, on a quantitative point of view, the enzymatic activity was particularly increased when R, F or A were in this position. The results allow us to define the P1' and P1 residues for an optimal substrate of pseudomonal serralysin and usable for the design and the synthesis of a specific inhibitor.