Biochemical aspects of a serine protease from Caesalpinia echinata Lam. (Brazilwood) seeds: a potential tool to access the mobilization of seed storage proteins.

Several proteins have been isolated from seeds of leguminous, but this is the first report that a protease was obtained from seeds of Caesalpinia echinata Lam., a tree belonging to the Fabaceae family. This enzyme was purified to homogeneity by hydrophobic interaction and anion exchange chromatographies and gel filtration. This 61-kDa serine protease (CeSP) hydrolyses H-D-prolyl-L-phenylalanyl-L-arginine-p-nitroanilide (K(m) 55.7 μM) in an optimum pH of 7.1, and this activity is effectively retained until 50 °C. CeSP remained stable in the presence of kosmotropic anions (PO(4) (3-), SO(4) (2-), and CH(3)COO(-)) or chaotropic cations (K(+) and Na(+)). It is strongly inhibited by TLCK, a serine protease inhibitor, but not by E-64, EDTA or pepstatin A. The characteristics of the purified enzyme allowed us to classify it as a serine protease. The role of CeSP in the seeds cannot be assigned yet but is possible to infer that it is involved in the mobilization of seed storage proteins.