Synthesis and hydrolysis by cathepsin B of fluorogenic substrates with the general structure benzoyl-X-ARG-MCA containing non-natural basic amino acids at position X.
We synthesized one series of fluorogenic substrates for cathepsin B derived from the peptide Bz-F-R-MCA (Bz=benzoyl, MCA=7-methyl-coumarin amide) substituting Phe at the P(2) position by non-natural basic amino acids that combine a positively charged group with aromatic or aliphatic radicals at the same side chain, namely, 4-aminomethyl-phenylalanine, 4-guanidine-phenylalanine, 4-aminomethyl-N-isopropyl-phenylalanine, 3-pyridyl-alanine, 4-piperidinyl-alanine, 4-aminomethyl-cyclohexyl-alanine, 4-aminocyclohexyl-alanine, and N(im)-dimethyl-histidine. Bz-F-R-MCA was the best substrate for cathepsin B but also hydrolyzed Bz-R-R-MCA with lower efficiency, since the protease accepts Arg at S(2) due to the presence of Glu(245) at the bottom of this subsite. The presence of the basic non-natural amino acids at the P(2) position of the substrate partially restored the catalytic efficiency of cathepsin B. All the kinetic parameters for hydrolysis of the peptides described in this paper are in accordance with the structures of the S(2) pocket previously described. In addition, the substrate with 4-aminocyclohexyl-alanine presented the highest affinity to cathepsin B although the peptide was obtained from a mixture of cis/trans isomers of the amino acid and we were not able to separate them. For comparison all the obtained substrates were assayed with cathepsin L and papain.
Melo
R L
RL
Department of Biophysics, Escola Paulista de Medicina, Universidade Federal de Sao Paulo, Brazil.
Barbosa Pozzo
R C
RC
Alves
L C
LC
Perissutti
E
E
Caliendo
G
G
Santagada
V
V
Juliano
L
L
Juliano
M A
MA
D000599:Amino Acids, Diamino / Q000138:chemical synthesis* / Q000737:chemistry; D002401:Cathepsin B / Q000737:chemistry*; D056668:Cathepsin L; D002403:Cathepsins / Q000737:chemistry; D003546:Cysteine Endopeptidases; D015195:Drug Design; D010450:Endopeptidases; D005456:Fluorescent Dyes / Q000138:chemical synthesis*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D015394:Molecular Structure; D010206:Papain / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry
D000599:Amino Acids, Diamino; D005456:Fluorescent Dyes; D010455:Peptides; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; C534281:CTSL protein, human; D056668:Cathepsin L; D010206:Papain