The specificity of two proteinases that cleave adjacent to arginine, C1 esterase and acrosin, for peptide p-nitroanilide substrates

• Published in: Biochimica et biophysica acta Vol. 996; no. 1-2; p. 89
• Main Authors: Skoog, M T, Mehdi, S, Wiseman, J S, Bey, P
• Format: Journal Article
• Language: English
• Published: Netherlands 13-06-1989
• Subjects: Acrosin - metabolism; Anilides - metabolism; Arginine - metabolism; Binding Sites; Citrulline - metabolism; Complement Activating Enzymes - metabolism; Complement C1s - metabolism; Humans; In Vitro Techniques; Kinetics; Lysine - metabolism; Peptides - metabolism; Serine Endopeptidases - metabolism; Substrate Specificity
• ISSN: 0006-3002

Relative values of Vmax/Km for hydrolysis of 40 peptide p-nitroanilides catalyzed by human Cl-s and human acrosin are reported. For Cl-s, Ac-Lys(gamma Cbz)-Gly-Arg is the optimum sequence, but 25% of the substrates have (Vmax/Km)rel greater than 0.25 compared to this sequence. The best acrosin substrate tested has the sequence Tos-Gly-Pro-Arg, although (Vmax/Km)rel greater than 0.15 for more than half of the substrates. Proline at P2 is preferred by acrosin. Both enzymes prefer arginine at P1 greater than or equal to 3-fold over lysine and will not accept citrulline. In addition, occupancy of site S3 may yield an increase in Vmax/Km of greater than or equal to 10-fold with either enzyme, but many residues are accepted at S2, S3 and S4. Thus, an acrosin assay using Tos-Gly-Pro-Arg p-nitroanilide as a substrate is more than 20-times as sensitive as existing assays with blocked arginine derivatives.