Cloning and heterologous expression of NAD(P)H : quinone reductase of Arabidopsis thaliana, a functional homologue of animal DT-diaphorase

In higher plants, NAD(P)H:quinone reductase (NQR) is the only flavoreductas e known to reduce quinone substrates directly to hydroquinones by a two-ele ctron reaction mechanism. This enzymatic activity is believed to protect ae robic organisms from the oxidative action of semiquinones, For this reason plant NQR has recently been suggested to be related to animal DT-diaphorase . A cDNA clone for NQR of Arabidopsis thaliana was identified, expressed in Escherichia coli, purified and characterized. Its amino acid sequence was found related to a number of putative proteins, mostly from prokaryotes, wi th still undetermined function. Conversely. in spite of the functional homo logy, sequence similarity between plant NQR and animal DT-diaphorase was li mited and essentially confined to the flavin binding site. (C) 1999 Federat ion of European Biochemical Societies.