Dihydrodipicolinate Reductases from Bacillus cereus and Bacillus megaterium

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Abstract
Dyhydrodipicolinate reductases were purified 100-fold from crude extracts of B. cereus and B. megaterium and their properties were compared with those of the reductase from B. sub-tilis. The molecular weights of the reductases of B. cereus and B. megaterium were found to be 155,000 and 150,000, respectively. These reductases were shown to be free of flavin, unlike the B. subtilis enzyme, which contains flavin. Both NADPH and NADH acted as coenzymes for these two reductases, NADPH being three or four times more effective than NADH. The Km values for NADPH and dihydrodipicolinate were 8 μM and 62 μM, respectively, with B. cereus reductase, and 13 μM and 59 μM with B. megaterium reductase. The pH optima of the enzymes from B. cereus and B. megaterium were pH 7.4 and 7.2, respectively. The reductases were inhibited by dipicolinate noncompetitively with respect to dihydrodipicolinate and the K1 values were 85 μM and 140 μM, respectively. Lysine and diaminopimelate were not inhibitory. The properties of the reductases from B. cereus and B. megaterium were similar, but they differed considerably from those of the B. subtilis enzyme. However, all three Bacillus reductases were markedly inhibited by dipicolinate, unlike the enzyme from E. coli.

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