Enzymatic characterization of an active NDH complex from Thermosynechococcus elongatus

•We purified an active NDH from Thermosynechococcus elongatus.•The active NDH contains both hydrophilic and hydrophobic subunits of NDH.•Ferredoxin and ferredoxin NADP+ oxidoreductase were co-eluted with the NDH.•The kinetic properties of the NDH were evaluated.•The active NDH is competitively inhibited by rotenone. Although type-1 NAD(P)H dehydrogenase (NDH) complex subunit constituents and physiological functions have been reported in plants and cyanobacteria, the biochemical properties of this enzyme are not clear. We used chromatographic isolation to purify and characterize a NADPH-active NDH from the cyanobacterium Thermosynechococcus elongatus. Ferredoxin (Fd) and ferredoxin-NADP+ oxidoreductase (FNR) were co-eluted with NDH, implying the electron donation from NADPH to NDH via the interaction with FNR. We investigated the enzymatic properties of the complex. Furthermore, the activity is competitively inhibited by rotenone, suggesting that it possesses a quinone binding site, similar to mitochondria complex I.