THE ASYMMETRIC SYNTHESIS OF PEPTIDE BONDS BY THE ACTION OF FICIN

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It has been reported (1) that papain as well as other papainase are capable of synthesizing CO-NH linkages especially in the meaning of antipodal specificity. It was desirable to see whether the ficin, a proteolytic enzyme of papain type, is capable of synthesizing peptide bonds or not.
We have now succeeded in the enzymatic synthesis of anilide or phenylhydrazide when in the presence of ficin acylated amino acid was incubated with aniline or phenylhydrazine at 37°C and pH 4.5.
The optimum pH range of the enzymatic formation of hippurylanilide has been found to be close to 4.5, at which the ficin is also able to perform hydrolysis.
It is remarkable that the antipodal specificity of the ficin as a synthesizing enzyme was revealed when acyl derivative of DL-phenylalanine was incubated with aniline and ficin. According to a very slight solubility of the anilide formed the antipodal specificity of the ficin can be utilized as a method to resolve DL-amino acids in their optical components.