A novel mode of lactate metabolism in strictly anaerobic bacteria

作者：Weghoff Marie Charlotte; Bertsch Johannes; Mueller Volker

来源：Environmental Microbiology, 2015, 17(3): 670-677.

DOI：10.1111/1462-2920.12493

Lactate is a common substrate for major groups of strictly anaerobic bacteria, but the biochemistry and bioenergetics of lactate oxidation is obscure. The high redox potential of the pyruvate/lactate pair of E-0=-190mV excludes direct NAD(+) reduction (E-0=-320mV). To identify the hitherto unknown electron acceptor, we have purified the lactate dehydrogenase (LDH) from the strictly anaerobic, acetogenic bacterium Acetobacterium woodii. The LDH forms a stable complex with an electron-transferring flavoprotein (Etf) that exhibited NAD(+) reduction only when reduced ferredoxin (Fd(2-)) was present. Biochemical analyses revealed that the LDH/Etf complex of A.woodii uses flavin-based electron confurcation to drive endergonic lactate oxidation with NAD(+) as oxidant at the expense of simultaneous exergonic electron flow from reduced ferredoxin (E-0 approximate to-500mV) to NAD(+) according to: lactate+Fd(2-)+2 NAD(+)pyruvate+Fd+2 NADH. The reduced Fd(2-) is regenerated from NADH by a sequence of events that involves conversion of chemical (ATP) to electrochemical and finally redox energy (Fd(2-) from NADH) via reversed electron transport catalysed by the Rnf complex. Inspection of genomes revealed that this metabolic scenario for lactate oxidation may also apply to many other anaerobes.

• 出版日期2015-3