S3 to S3' subsite specificity of recombinant human cathepsin K and development of selective internally quenched fluorescent substrates.
We have systematically examined the S3 to S3' subsite substrate specificity requirements of cathepsin K using internally quenched fluorescent peptides derived from the lead sequence Abz-KLRFSKQ-EDDnp [where Abz is o -aminobenzoic acid and EDDnp is N -(2,4-dinitrophenyl)ethylenediamine]. We assayed six series of peptides, in which each position except Gln was substituted with various natural amino acids. The results indicated that the S3-S1 subsite requirements are more restricted than those of S1'-S3'. Cathepsin K preferentially accommodates hydrophobic amino acids with aliphatic side chains (Leu, Ile and Val) in the S2 site. Modifications at P1 residues also have a large influence on cathepsin K activity. Positively charged residues (Arg and Lys) represent the best accepted amino acids in this position, although a particular preference for Gly was found as well. Subsite S3 accepted preferentially basic amino acids such as Lys and Arg. A broad range of amino acids was accommodated in the remaining subsites. We further explored the acceptance of a Pro residue in the P2 position by cathepsin K in order to develop specific substrates for the enzyme. Two series of peptides with the general sequences Abz-KXPGSKQ-EDDnp and Abz-KPXGSKQ-EDDnp (where X denotes the position of the amino acid that is altered) were synthesized. The substrates Abz-KPRGSKQ-EDDnp and Abz-KKPGSKQ-EDDnp were cleaved by cathepsin K at the Arg-Gly and Gly-Ser bonds respectively, and have been shown to be specific for cathepsin K when compared with other lysosomal cysteine proteases such as cathepsins L and B and with the aspartyl protease cathepsin D.
Alves
Marcio F M
MF
Department of Biophysics, Escola Paulista de Medicina, UNIFESP, Rua Três de Maio 100, São Paulo 04044-020, Brazil.
Puzer
Luciano
L
Cotrin
Simone S
SS
Juliano
Maria Aparecida
MA
Juliano
Luiz
L
Brömme
Dieter
D
Carmona
Adriana K
AK
D000595:Amino Acid Sequence; D001920:Bradykinin / Q000378:metabolism; D056657:Cathepsin K; D002403:Cathepsins / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism*; D006801:Humans; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity
D005456:Fluorescent Dyes; D011994:Recombinant Proteins; D002403:Cathepsins; C534130:CTSK protein, human; D056657:Cathepsin K; D001920:Bradykinin