Membrane-bound l- and d-lactate dehydrogenase activities of a newly isolated Pseudomonas stutzeri strain

Abstract

Pseudomonas stutzeri SDM was newly isolated from soil, and two stereospecific NAD-independent lactate dehydrogenase (iLDH) activities were detected in membrane of the cells cultured in a medium containing DL-lactate as the sole carbon source. Neither enzyme activities was constitutive, but both of them might be induced by either enantiomer of lactate. P. stutzeri SDM preferred to utilize lactate to growth, when both L-lactate and glucose were available, and the consumption of glucose was observed only after lactate had been exhausted. The Michaelis-Menten constant for L-lactate was higher than that for D-lactate. The L-iLDH activity was more stable at 55 degrees C, while the D-iLDH activity was lost. Both enzymes exhibited different solubilization with different detergents and different oxidation rates with different electron acceptors. Combining activity staining and previous proteomic analysis, the results suggest that there are two separate enzymes in P. stutzeri SDM, which play an important role in converting lactate to pyruvate.

Lactate Utilization Is Regulated by the FadR-Type Regulator LldR in Pseudomonas aeruginosa

“…Unlike the situation in E. coli and C. glutamicum, D-iLDH and L-iLDH are induced coordinately in these Pseudomonas strains (12,21,22). Neither of the enzymes is constitutively expressed, and either enantiomer of lactate can induce the expression of both enzymes (12,21,22). These results indicate that the iLDH regulatory mechanism in Pseudomonas strains may be different from the wellstudied mechanism in E. coli and C. glutamicum.…”

“…Unlike the situation in E. coli and C. glutamicum, D-iLDH and L-iLDH are induced coordinately in these Pseudomonas strains (12,21,22). Neither of the enzymes is constitutively expressed, and either enantiomer of lactate can induce the expression of both enzymes (12,21,22).…”

“…M201024). For the growth experiments, iLDH activity determination, and RNA isolation experiments, strain XMG was cultured in 500-ml baffled shake flasks containing lysogeny broth (LB) medium (3) or minimal salt medium (MSM) (22) at 37°C and 120 rpm. MSM was supplemented with 5.0 g/liter DL-lactate or pyruvate as the sole carbon source.…”

“…Utilization of lactate has also been studied in different Pseudomonas strains, such as Pseudomonas aeruginosa, Pseudomonas putida, and Pseudomonas stutzeri (5,12,21,22,27). Unlike the situation in E. coli and C. glutamicum, D-iLDH and L-iLDH are induced coordinately in these Pseudomonas strains (12,21,22).…”

“…any bacteria can use lactate as the sole carbon and energy source for growth (9,16,17,22,30). NAD-independent lactate dehydrogenases (iLDHs), which catalyze the oxidation of lactate to pyruvate via a flavin-dependent mechanism, play an essential role in the utilization of lactate in most lactate-utilizing bacteria (8,15,16,17).…”