* To whom correspondence should be addressed.
Received July 14, 2007
Structural and functional peculiarities of four types of nitrate reductases are considered: assimilatory nitrate reductase of eukaryotes, as well as cytoplasmic assimilatory, membrane-bound respiratory, and periplasmic dissimilatory bacterial nitrate reductases. Arguments are presented showing that eukaryotic organisms are capable of nitrate dissimilation. Data concerning new classes of extremophil nitrate reductases, whose active center does not contain molybdocofactor, are summarized.
KEY WORDS: nitrate reductase, nitrification, denitrification, molybdenum, molybdenum cofactor, molybdopterin-guanine dinucleotides, stress