The condensation step in diaminopimelate synthesis.

Previous studies of the pathway of biosynthesis of diaminopimelic acid had indicated that pyruvic acid (1) and aspartic semialdehyde (2) were sources of the carbon skeleton of diaminopimelic acid. In addition, N-succinyl-cY-amino-e-ketopimelic acid had been established as an intermediary in the biosynthesis (3, 4). A comparison of the structures of these precursors and this intermediary (Fig. 1) indicated the existence in the pathway of steps involving condensation of the carbon chains of the precursors, reduction at the point of juncture, and a succinylation of the amino group. However, this analysis provided no information as to the sequence of these reactions. One possible sequence, suggested by the biosynthetic pathway leading to ornithine (5), would formulate N-succinylaspartic semialdehyde as an intermediate. This compound was synthesized but proved to be inactive.’ Another alternative, the direct condensation of pyruvate and aspartic semialdehyde, was then explored. An enzyme catalyzing such a reaction was detected in Escherichia coZi extracts. The part.ial purification and some of the properties of this enzyme are described. A preliminary communication of these results has appeared (6).