A Lewis-acid-catalyzed method for the substrate-directed formation of peptide bonds has been developed, and this powerful approach is utilized for the new "remote" activation of carboxyl groups under solvent-free conditions. The presented method has the following advantages: 1) the high-yielding peptidesynthesis uses a tantalum catalyst for any amino acids; 2) the reaction proceeds without any racemization;
Two 7-amino-4-methylcoumarinamide derivatives of tripeptides were synthesized. They were shown to be potentially useful substrates for fluorometric microdetermination of subtilisins BPN'and Carlsberg. The kinetic characteristics of the hydrolyses of these substrates by the enzymes were investigated.
An endopeptidase (Cudrania protease) with a molecular mass of 76 kDa has been purified from the fruits of Cudrania cochinchinensis (Lour.) Kudo et Masam. The enzyme was stable between pH 6 and 10 at 30°C for 60 min. The enzyme activity was inhibited by diisopropyl fluorophosphate, chymostatin, and aprotinin, but not by EDTA or pepstatin. These results indicated that the enzyme was a serine protease.