Alternative, nonproton pumping NADH:quinone oxidoreductase that delivers electrons to the respiratory chain by oxidation of NADH and reduction of quinones (PubMed:15767566, PubMed:29382761, PubMed:29522317). Ndh is probably the main NADH dehydrogenase of M.tuberculosis (PubMed:29382761). a quinone + H(+) + NADH = a quinol + NAD(+) a menaquinone + H(+) + NADH = a menaquinol + NAD(+) a ubiquinone + H(+) + NADH = a ubiquinol + NAD(+) Binds 1 FAD per subunit. Inhibited by phenothiazine analogs (PubMed:15767566). Inhibited by 2-mercapto-quinazolinones (PubMed:29522317). Not inhibited by classic inhibitors of type I NADH dehydrogenase, such as rotenone, piericidin A and pyridaben (PubMed:15767566). Deletion mutant is attenuated for growth and virulence in mice (PubMed:29382761). Deletion of the gene alters the NADH/NAD(+) ratio, suggesting that this enzyme has an important function in maintaining the redox status of the cell (PubMed:29382761). Mutant shows growth defects in vitro and is more susceptible to oxidative stress reagents, but not to potential NADH dehydrogenase inhibitors (PubMed:29382761). Was considered as an essential gene in vitro, but later studies show that ndh is not essential individually (PubMed:25128581, PubMed:29382761). The ndh-ndhA double knockout could not be obtained, suggesting that at least one type II NADH dehydrogenase is required for M.tuberculosis growth (PubMed:29382761). Belongs to the NADH dehydrogenase family.