Synthetic peptides and fluorogenic substrates related to the reactive site sequence of Kunitz-type inhibitors isolated from Bauhinia: Interaction with human plasma kallikrein

We have previously described Kunitz-type serine proteinase inhibitors purified from Bauhinia seeds. Human plasma kallikrein shows different susceptibility to those inhibitors. In this communication, we describe the interaction of human plasma kallikrein with fluorogenic and non-fluorogenic peptides based on the Bauhinia inhibitors' reactive site. The hydrolysis of the substrate based on the a. variegata inhibitor reactive site sequence, Abz-WISALPRSVFIQ-EDDnp (K-m 1.42 muM, k(cat) 0.06 s(-1), and k(cat)/K-m 4.23 x 10(4) M-1 s(-1)), is more favorable than that of Abz-VMIAALPRTMFIQ-EDDnp, related to the B. ungulata sequence (K-m 0.43 muM, k(cat) 0.00017 s(-1), and k(cat)/K-m 3.9 x 10(2) M-1 s(-1)). Human plasma kallikrein does not hydrolyze the substrates Abz-RPGLPVRFESPL-EDDnp and Abz-FESPLRINIIKE-EDDnp based on the a. bauhinioides inhibitor reactive site sequence, the most effective inhibitor of the enzyme. These peptides are competitive inhibitors with K-i values in the nM range. The synthetic peptide containing 19 amino acids based on the a. bauhinioides inhibitor reactive site (RPGLPVRFESPL) is poorly cleaved by kallikrein. The given substrates are highly specific for trypsin and chymotrypsin hydrolysis. Other serine proteinases such as factor Xa, factor XII, thrombin and plasmin do not hydrolyze a. bauhinioides inhibitor related substrates.Univ Fed Sao Paulo, Escola Paulista Med, Dept Bioquim, BR-04044020 Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Dept Biofis, BR-04044020 Sao Paulo, BrazilEMBRAPA, Empresa Brasileira Pesquisa Agropecuaria, BR-79320900 Corumba, MS, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Dept Bioquim, BR-04044020 Sao Paulo, BrazilUniv Fed Sao Paulo, Escola Paulista Med, Dept Biofis, BR-04044020 Sao Paulo, BrazilWeb of Scienc