Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.4 (nitrite reductase)
 1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interactions of ferredoxin-linked nitrite reductase (NiR) from spinach with its substrate were studied by spectrophotometry and electron spin resonance (ESR) spectroscopy. Siroheme was extractable from NiR with 2.5% (W/V) trichloroacetic acid (TCA) and with acetone containing 0.01 N HCl. The addition of nitrite or sulfite to these extracts resulted in shifts of the absorption spectra of siroheme. The HCl-acetone extract showed ESR signals of symmetrical high spin heme, which disappeared on addition of nitrite. Spectral titration indicated a high affinity of extracted siroheme to nitrite and sulfite. The addition of nitrite or sulfite to protoheme dissolved in 0.01 N HCl-acetone did not cause a shift of the absorption spectrum. The extractability of siroheme with 0.01 N HCl-acetone was suppressed by the addition of nitrite to the NiR preparation. Moreover, a substrate-induced difference spectrum with peaks at about 295 and 287 nm was observed on addition of nitrite to NiR. These observations indicated an intrinsic strong affinity of siroheme to nitrite and sulfite, formation of rhombicity of siroheme by binding to the protein moiety, and also a probable conformational change of NiR on binding to the substrate. In agreement with previous reports, ESR signals of the heme-NO complex were observed with NiR in the presence of nitrite, methyl viologen (MV), and dithionite. In the present study, the same signals of similar intensity were also observed on omission of MV, under which conditions no catalytic reduction of nitrite occurred. Furthermore, the signal of the heme-NO complex was not observed when MV was replaced by spinach ferredoxin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Spectrophotometric and electron spin resonance studies on the substrate interactions of ferredoxin-linked nitrite reductase from spinach. 632 82

Nitrite reductase from Pseudomonas aeruginosa (EC 1.9.3.2), a redox enzyme synthesized by the bacterium grown in the presence of nitrate, is a soluble dimer of two identical subunits of 60 kDa, each containing one c and one d1 haem as prosthetic groups. A new crystal from of the Ps. aeruginosa nitrite reductase in the oxidized state, suitable for X-ray structure determination, has been obtained by vapour diffusion at 20 degrees C, in the presence of 10% polyethylene glycol 4000, 50 mM Tris-HCl (pH 8.7), 400 mM NaCl and at a protein concentration of 14 mg/ml. The crystals are dark green elongated tetragonal prisms of dimensions 1.5 mm x 0.2 mm x 0.2 mm for the largest ones. These crystals are tetragonal with space group P4(1(3))2(1)2 and cell dimensions a = b = 128.2 A, c = 172.6 A. They diffract at least up to 2.8 A. Assuming a dimer in the asymmetric unit, the VM value is 2.95 A3/Da (58% of solvent).
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PMID:Crystallization and preliminary X-ray analysis of a new crystal form of nitrite reductase from Pseudomonas aeruginosa. 793 60