PARAQUAT DIAPHORASES IN ESCHERICHIA-COLI

Extracts of E. coli contain at least three easily separable NAD(P)H:paraquat diaphorases. One of these is identified as thioredoxin reductase, which accounts for most of the PQ(++) diaphorase in a thioredoxin reductase overproducer but is only 25% of this activity in a wild type. NADP(+), but not NAD(+), inhibited the diaphorase activity of thioredoxin reductase. All of the soluble PQ(++) diaphorases of E. coli are stable during fractionation by HPLC and none depend upon the cooperative action of components separable by this technique. GSSG reductase is inhibited by PQ(++) and is not, to any significant degree, a contributor to the diaphorase activity of E. coli.