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Luciano Puzer, Simone S. Cotrin, Maria H.S. Cezari, Izaura Y. Hirata, Maria A. Juliano, Ivica Stefe, Dusan Turk, Boris Turk, Luiz Juliano, Adriana K. Carmona

Recombinant human cathepsin X is a carboxymonopeptidase only: a comparison with cathepsins B and L

Keywords: carboxymonopeptidase, cathepsin B, cathepsin L, cathepsin X, lysosomal cathepsins, selective substrate, specificity studies

The S₁ and S₂ subsite specificity of recombinant human cathepsins X was studied using fluorescence resonance energy transfer (FRET) peptides with the general sequences Abz-Phe-Xaa-Lys(Dnp)-OH and Abz-Xaa-Arg-Lys(Dnp)-OH, respectively (Abz=ortho-aminobenzoic acid and Dnp=2,4-dinitrophenyl; Xaa=various amino acids). Cathepsin X cleaved all substrates exclusively as a carboxymonopeptidase and exhibited broad specificity. For comparison, these peptides were also assayed with cathepsins B and L. Cathepsin L hydrolyzed the majority of them with similar or higher catalytic efficiency than cathepsin X, acting as an endopeptidase mimicking a carboxymonopeptidase (pseudo-carboxymonopeptidase). In contrast, cathepsin B exhibited poor catalytic efficiency with these substrates, acting as a carboxydipeptidase or an endopeptidase. The S₁? subsite of cathepsin X was mapped with the peptide series Abz-Phe-Arg-Xaa-OH and the enzyme preferentially hydrolyzed substrates with hydrophobic residues in the P₁? position.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 386, 11/2005
Pages: 1191 - 1195

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