ISOLATION AND PRELIMINARY CHARACTERIZATION OF A SOLUBLE NITRATE REDUCTASE FROM THE SULFATE-REDUCING ORGANISM DESULFOVIBRIO-DESULFURICANS ATCC-27774

Desulfovibrio desulfuricans ATCC 27774 is a sulfate reducer that can adapt to nitrate respiration, inducing the enzymes required to utilize this alternative metabolic pathway. Nitrite reductase from this organism has been previously isolated and characterized, but no information was available on the enzyme involved in the reduction of nitrate. This is the first report of purification to homogeneity of a nitrate reductase from a sulfate reducing organism, thus completing the enzymatic system required to convert nitrate (through nitrite) to ammonia. D, desulfuricans nitrate reductase is a monomeric (circa 70 kDa) periplasmic enzyme with a specific activity of 5.4 K-m for nitrate was estimated to be 20 mu M. EPR signals due to one [4Fe-4S] cluster and Mo(V) were identified in dithionite reduced samples and in the presence of nitrate.