Two catalytically distinct molybdenum-free dissimilatory nitrate reductases
, a soluble periplasmic and a membrane-bound one, were isolated from the va
nadate-reducing facultatively anaerobic bacterium Pseudomonas isachenkovii
and purified to electrophoretic homogeneity, The enzymes did not contain mo
lybdenum, the periplasmic enzyme contained vanadium, whereas the membrane-b
ound enzyme was vanadium-free. Both nitrate reductases lacked molybdenum co
factor. This fact was proved by reconstitution of the apoprotein of the nit
rate reductase of Neurospora crassa nit-1 mutant. This is the first demonst
ration of molybdenum-free and molybdenum cofactor-free nitrate reductases.
(C) 1998 Federation of European Biochemical Societies.