Three mycobacterial strains isolated from fish degraded putrescine by a pathway in which γ-aminobutyraldehyde (Δ′-pyrroline), γ-aminobutyric acid, succinic semialdehyde, and succinic acid were intermediates. These results agree substantially with those of other workers using different microorganisms. Intact cells utilized γ-aminobutyric acid in a transaminase reaction with endogenously supplied α-ketoglutarate to produce succinic semialdehyde and glutamate. Studies with arsenite-poisoned cells showed that a significant proportion of putrescine was metabolized via pyruvate and alanine. When putrescine-1,4-14C was substrate, HCl extracts of cells contained radioactive aspartate and glutamate in addition to alanine. The further metabolism of succinate therefore proceeded in two directions: one yielding oxalacetate and α-ketoglutarate by way of the tricarboxylic acid cycle, and the other branching off the cycle to yield pyruvate. Studies with cell-free extracts suggested that putrescine nitrogen was assimilated via glutamate, which served as the amino-group donor to yield alanine and aspartate.
γ-Aminobutyric Acid Pathway and Modified Tricarboxylic Acid Cycle Activity During Growth and Sporulation of Bacillus thuringiensis
