title: Purification and some properties of the nitrite reductase from the cyanobacterium Phormidium laminosum.
abstract: Assimilatory ferredoxin-nitrite reductase (EC 1.7.7.1, ammonia: ferredoxin oxidoreductase) has been purified 5300-fold with a specific activity of 625 units/mg protein from the filamentous non-heterocystous cyanobacterium Phormidium laminosum. The enzyme was soluble and consisted of a single polypeptidic chain of 54 kDa. It catalyzed the reduction of nitrite to ammonia using ferredoxin or flavodoxin as electron donor. Methyl and benzyl viologens were also effective as electron donors but neither flavins nor NAD(P)H were. The apparent Michaelis constants for nitrite, ferredoxin and methyl viologen were 40, 22 and 215 microM, respectively. Nitrite reductase activity was inhibited effectively by cyanide and thiol reagents. The enzyme exhibited absorption maxima at 281, 391 (Soret), 570 (alpha) and 695 nm, with epsilon 391 of 4.3 x 10(4) M-1 cm-1, and an absorbance ratio A281/A391 of 1.95, suggesting the presence of siroheme as prosthetic group. These results show that this enzyme is similar to those of eukaryotic organisms.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco, Bilbao, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Arizmendi
authors.forename: J L
authors.initials: JL
authors.lastname: Serra
mesh_terms: D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D000458:Cyanobacteria / Q000201:enzymology*; D005288:Ferredoxins / Q000302:isolation & purification / Q000378:metabolism; D005418:Flavodoxin / Q000302:isolation & purification / Q000378:metabolism; D007202:Indicators and Reagents; D007700:Kinetics; D008970:Molecular Weight; D009247:NADH, NADPH Oxidoreductases / Q000302:isolation & purification*; D009572:Nitrite Reductases / Q000302:isolation & purification* / Q000378:metabolism; D013053:Spectrophotometry; D013379:Substrate Specificity
chemical_list: D005288:Ferredoxins; D005418:Flavodoxin; D007202:Indicators and Reagents; D009247:NADH, NADPH Oxidoreductases; D009572:Nitrite Reductases