4-amino-4-cyanobutyric acid as an intermediate in glutamate biosynthesis.

A novel compound, 4-amino-4-cyanobutyric acid, was isolated and identitled from cultures of an unidentified psychrophilic basidiomycete. Triple labeling experiments in vivo involving the simultaneous administration of KW15N and succinic semialdehydeJ4C to fungus cultures showed that these compounds along with ammonia are precursors of 4amino-4-cyanobutyric acid. In addition, cell-free extracts were able to catalyze this reaction. That 4-amino-4-cyanobutyric acid is a precursor of glutamate was also established by triple labeling experiments as well as with crude enzyme preparations. In the latter case nitrilase activity was demonstrated. Enzymes involved in glutamate and succinic semialdehyde metabolism were found, and on this basis a cycle involving cyanide detoxification is proposed.