Escherichia coli dihydrodipicolinate synthase and dihydrodipicolinate reductase: kinetic and inhibition studies of two putative herbicide targets

Dihydrodipicolinate synthase (DHDPS) (EC 4.2.1.52) and dihydrodipicolinate reductase (DHDPR) (EC 1.3.1.26) have attracted much recent attention as potential herbicide targets. DHDPS was feedback-inhibited by Q-lysine; inhibition was reversible and uncompetitive with respect to both (S)-ASA and pyruvate. Homoserine lactone was a reversible non-competitive inhibitor of DHDPS with respect to both (S)-ASA and pyruvate. (R)-Cysteine sulfinic acid and (S)-glutamic acid were reversible uncompetitive inhibitors of DHDPS with respect to Q-ASA. (S)-Aspartic acid was a reversible mixed-type inhibitor. Dipicolinic acid was a reversible competitive inhibitor of DHDPR with respect to the substrate (4S)-4-hydroxy-2,3,4,5-tetrahydro-(2S)-dipicolinic acid, as was isophthalic acid. Delta(3)-Tetrahydroisophthalic acid was a moderate inhibitor of both DHDPS and DHDPR, These compounds represent possible leads in the development of novel herbicides. (C) 1999 Society of Chemical Industry.