Chemical Modification of Amino Groups in Alanine Dehydrogenase from Bacillus natto KMD 1126

抄録

Amino groups of alanine dehydrogenase from Bacillus natto KMD 1126 were modified by treatment with 2, 4, 6-trinitrobenzenesulfonic acid (TNBS) ; this resulted in loss of the enzyme activity with pseudo first order kinetics. However, sulfhydryl groups were not modified by TNBS, and the circular dichroism spectrum of the TNBS-modified enzyme was identical with that of the native enzyme. Complete inactivation was obtained upon modification of 5 amino groups per subunit of the enzyme. However, a plot of log [reciprocal of the half-time of inactivation] versus log [concentration of TNBS] suggested that one amino group has an essential role in the catalysis. Protection against inactivation by TNBS was not observed on the addition of nicotinamide adenine dinucleotide or its reduced form.