Cell-free extracts of Brevibacterium sp. L5 grown on DL-erythro-3,5-diaminohexanoate were found to contain a 3-keto-5-aminohexanoate cleavage enzyme that converts 3-keto-5-aminohexanoate and acetyl-coenzyme A (CokA) to 3-aminobutyryl-CoA and acetoacetate and a deaminase that coverts L-3-aminobutyryl-CoA to crotonyl-CoA. The cleavage enzyme has been purified extensively, and some of its properties have been determined for comparison with the 3-keto-6-acetamido-hexanoate cleavage enzyme of Pseudomonas sp. B4. The deaminase has been partially purified and characterized. Both the cleavage enzyme and the deaminase are induced by growth on 3,5-diaminohexanoate. The presence of these and other accessory enzymes in Brevibacterium sp. extracts accounts for the results of earlier tracer experiments which showed that C-1 and C-2 of 3-keto-5-aminohexanoate are converted mainly to acetoacetate and acetate, whereas C-3 to C-6 are converted mainly to 3-hydroxybutyrate or its coenzyme A thiolester. The enzymes observed in extracts of Brevibacterium sp. can account for the conversion of 3,5-diaminohexanoate to acetyl-CoA.