抄録
Three reactants, aminomethylpyridine, α-keto acid and divalent metal ion were mixed in methanol and formation of metal chelate of aldimine was followed by changes of electronic absorption spectra. Aminomethylpyridines used were pyridoxamine and 3-hydroxy-4-aminomethylpyridine ; α-keto acids were Na pyruvate, Na α-ketobutyrate, K α-ketoisovalerate, ethyl pyruvate and ethyl α-ketobutyrate ; metal ions were Zn (II), Ni (II) and Cu (II). Every combination of the substances were examined. Analyses of spectral changes showed that the reactions consisted of two slow steps, ketimine metal chelate formation from the three reactants and its isomerization to aldimine metal chelate. In reactions with Zn (II) ion, the isomerization step was rate determining, while in reactions with Ni (II) ion ketimine chelate formation became slower step. By chelation with Cu (II). ketimine chelate formation was retarded but the isomerization was accelerated. Ketimine formation was faster with esters of keto acid than with anions. In the anions rate of ketimine formation was pyruvate>α-ketobutyrate>α-ketoisovalerate in the presence and in the absence of the metal ions. None of the combination of the reactants in the present study produced an intermediate absorbing in the 500-nm region.
