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Literature summary for 1.7.7.2 extracted from

  • Kilic, V.; Kilic, G.A.; Kutlu, H.M.; Martinez-Espinosa, R.M.
    Nitrate reduction in Haloferax alexandrinus: the case of assimilatory nitrate reductase (2017), Extremophiles, 21, 551-561.
    View publication on PubMed

Inhibitors

Inhibitors Comment Organism Structure
azide 1 mM, 90% inhibition Haloferax alexandrinus
cyanide 1 mM, 98% inhibition Haloferax alexandrinus
EDTA 1 mM, 52% inhibition Haloferax alexandrinus
sulfite 1 mM, 30% inhibition Haloferax alexandrinus

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
0.045
-
nitrate 120 mM Na2CO3 pH 9, 1 M NaCl, 4 mM methyl viologen, 35 mM KNO3, 17 mM Na2S2O4 (freshly prepared in 0.1 M NaHCO3) and 0.7 mU of enzyme preparations. The samples are incubated for 20 min at 60°C Haloferax alexandrinus
0.0646
-
reduced methyl viologen 120 mM Na2CO3 pH 9, 1 M NaCl, 4 mM methyl viologen, 35 mM KNO3, 17 mM Na2S2O4 (freshly prepared in 0.1 M NaHCO3) and 0.7 mU of enzyme preparations. The samples are incubated for 20 min at 60°C Haloferax alexandrinus

Metals/Ions

Metals/Ions Comment Organism Structure
iron-sulfur centre
-
Haloferax alexandrinus
KCl up to 2 M, the highest the salt concentration, the highest the activity value. Activity is significantly higher in the presence of KCl than in the presence of NaCl Haloferax alexandrinus
NaCl up to 2 M, the highest the salt concentration, the highest the activity value. Activity is significantly higher in the presence of KCl than in the presence of NaCl Haloferax alexandrinus

Molecular Weight [Da]

Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
72000
-
-
Haloferax alexandrinus

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
nitrate + 2 reduced ferredoxin + 2 H+ Haloferax alexandrinus the enzyme is involved in aerobic assimilatory nitrate reduction. The enzyme enables Haloferax alexandrinus to use nitrate as sole nitrogen source for growth under aerobic conditions. Haloferax alexandrinus may induce denitrification under anaerobic or microaerobic conditions using nitrate as electron acceptor nitrite + H2O + 2 oxidized ferredoxin
-
?
nitrate + 2 reduced ferredoxin + 2 H+ Haloferax alexandrinus JCM 10717 the enzyme is involved in aerobic assimilatory nitrate reduction. The enzyme enables Haloferax alexandrinus to use nitrate as sole nitrogen source for growth under aerobic conditions. Haloferax alexandrinus may induce denitrification under anaerobic or microaerobic conditions using nitrate as electron acceptor nitrite + H2O + 2 oxidized ferredoxin
-
?

Organism

Organism UniProt Comment Textmining
Haloferax alexandrinus M0HXK1
-
-
Haloferax alexandrinus JCM 10717 M0HXK1
-
-

Purification (Commentary)

Purification (Comment) Organism
-
Haloferax alexandrinus

Storage Stability

Storage Stability Organism
4°C, activity decreases about 40% in 1 week when the crude extract is stored. At temperatures higher than 4°C, the activity depletion in the crude extract is 60–80% Haloferax alexandrinus
4°C, the activity of the pure sample is stable for 2–3 weeks Haloferax alexandrinus

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
nitrate + 2 reduced ferredoxin + 2 H+ the enzyme is involved in aerobic assimilatory nitrate reduction. The enzyme enables Haloferax alexandrinus to use nitrate as sole nitrogen source for growth under aerobic conditions. Haloferax alexandrinus may induce denitrification under anaerobic or microaerobic conditions using nitrate as electron acceptor Haloferax alexandrinus nitrite + H2O + 2 oxidized ferredoxin
-
?
nitrate + 2 reduced ferredoxin + 2 H+ the enzyme is involved in aerobic assimilatory nitrate reduction. The enzyme enables Haloferax alexandrinus to use nitrate as sole nitrogen source for growth under aerobic conditions. Haloferax alexandrinus may induce denitrification under anaerobic or microaerobic conditions using nitrate as electron acceptor Haloferax alexandrinus JCM 10717 nitrite + H2O + 2 oxidized ferredoxin
-
?
nitrate + reduced methyl viologen reduced methyl viologen is the best electron donor. No activity with either NADH (1 mM) or NADPH (1 mM) (in the presence or absence of dithionite within the reaction mixture). Dithionite is not able to reduce nitrate in the absence of reduced methyl viologen Haloferax alexandrinus nitrite + H2O + oxidized methyl viologen
-
?
nitrate + reduced methyl viologen reduced methyl viologen is the best electron donor. No activity with either NADH (1 mM) or NADPH (1 mM) (in the presence or absence of dithionite within the reaction mixture). Dithionite is not able to reduce nitrate in the absence of reduced methyl viologen Haloferax alexandrinus JCM 10717 nitrite + H2O + oxidized methyl viologen
-
?

Subunits

Subunits Comment Organism
monomer 1 * 72000, SDS-PAGE, taking into account that molecular masses of halophilic proteins are overestimated in SDS-PAGE (around 13–17%) a molecular mass of around 70000 would be expected Haloferax alexandrinus
monomer 1 * 76050, calculated from nucleotide sequence Haloferax alexandrinus

Temperature Optimum [°C]

Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
50
-
the enzyme shows a remarkable thermophilicity and works well up to 50°C in the presence of high salt concentrations Haloferax alexandrinus

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
9.5
-
-
Haloferax alexandrinus

pH Range

pH Minimum pH Maximum Comment Organism
5 11 pH 5.0: about 50% of maximal activity, pH 11.0: about 80% of maximal activity Haloferax alexandrinus

Cofactor

Cofactor Comment Organism Structure
iron-sulfur centre
-
Haloferax alexandrinus

pI Value

Organism Comment pI Value Maximum pI Value
Haloferax alexandrinus calculated from amino acid sequence
-
4.52

Expression

Organism Comment Expression
Haloferax alexandrinus activity is detected between 72 and 168 h of incubation, and it reaches the maximum value when the absorbance of the culture is around 0.47 (at 600 nm). This maximum activity value is observed shortly after the beginning of the exponential phase of growth, and in that moment, high nitrite concentration within the media is quantified (up to 18.8 mM). This growth phase is characterised by oxygen depletion (culture medium is initially aerobic, but it becomes microaerobic as soon as the biomass increases shortly before the stationary phase of growth) up