| Autor: |
Cotrin SS; Department of Biophysics, Escola Paulista de Medicina, UNIFESP, Rua Três de Maio, 100, São Paulo 04044-020, Brazil., Puzer L, de Souza Judice WA, Juliano L, Carmona AK, Juliano MA |
| Abstrakt: |
We have developed positional scanning synthetic combinatorial libraries to define the substrate specificity of carboxydipeptidases. The library Abz-GXXZXK(Dnp)-OH, where Abz is ortho-aminobenzoic acid, K(Dnp) is N(epsilon)-2,4-dinitrophenyl-lysine with free carboxyl group, the Z position was successively occupied with 1 of 19 amino acids (cysteine was omitted), and X represents randomly incorporated residues, was assayed initially with human cathepsin B, and arginine was defined as one of the best residues at the P(1) position. To examine the selectivity of S(1)('), S(2), and S(3) subsites, the sublibraries Abz-GXXRZK(Dnp)-OH, Abz-GXZRXK(Dnp)-OH, and Abz-GZXRXK(Dnp)-OH were then synthesized. The peptide Abz-GIVRAK(Dnp)-OH, which contains the most favorable residues in the P(3)-P(1)(') positions identified by screening of the libraries with cathepsin B, was hydrolyzed by this enzyme with k(cat)/K(m)=7288 mM(-1)s(-1). This peptide is the most efficient substrate described for cathepsin B to this point, and it is highly selective for the enzyme among the lysosomal cysteine proteases. |
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