A study of the metabolism of L-L, y-diamino-butyric acid in a Xanthomonas species.

1. L.o::y.Diaminobutyric acid is metabolized in Xanl1wmonas sp. to aspartic
,B.semialdehyde, aspartic acid and oxaloacetic acid. 2. Aspartic ,B.semialdehyde is
fonned from diaminobutyric acid by a. pyruvate-dependent y-transamination.
3. The transaminase has a pH optimum of 9 and exhibits a high degree of substrate
specificity, as analogues of diaminobutyric acid and pyruvate are inert in the
system. The transaminase is inhibited bycarbonyl.binding agents such a.<; hydroxylamine.
4. Aspartic acid is fonned from aspaxt,ic ,B.semialdehyde by an NAD+·
dependent dehydrogenation. 5. The dehydrogenase has a pH optimum of8·5 and is
a thiol enzyme. It is specific for aspartic ,B.semialdehyde but analogues of NAD+
such as 3-acetylpyrid.ine~adeninedinucleotide and deamino-NAD are partly active
in the system. 6. The significance of these reactions is discussed in relation to
diaminobutyric acid metabolism in plants ami mammalian systems.