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German to English - Standard rate: 0.11 USD per word / 25 USD per hour
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Sample translations submitted: 1
German to English: Nitritreduktion Detailed field: Biology (-tech,-chem,micro-)
Source text - German Die Denitrifikation von Nitrat erfolgt bei vollständiger Reaktion über die Zwischenstufen Nitrit - NO - N2O zu molekularem Stickstoff. Für jeden Schritt gibt es eine Reduktase. In fakultativ anaeroben Bakterien ist die Nitratreduktase ein Transmembranprotein, das mit einem Nitrat/Nitrit-Antiporter assoziiert ist. Das Reaktionsprodukt Nitrit wird in den periplasmatischen Raum abgegeben, wo die Enzyme für die nächsten beiden Reaktionsschritte lokalisiert sind (Nitrit und NO führen im Cytoplasma zu Vergiftungserscheinungen).
Bisher sind zwei Klassen dissimilatorischer Nitritreduktasen bekannt: Die Enzyme der Klasse I enthalten Kupfer als Kofaktor, bei Klasse II wird Häm benutzt. Bei der Ammonifizierung (andere Seite des Stickstoffkreislaufes) gibt es hexahämhaltige Nitritreduktasen. Die molekularen Strukturen von Klasse I und Klasse II - Enzymen konnte aufgeklärt werden.
Klasse II - Enzyme katalysieren sowohl die ein-Elektron-Reduktion von Nitrit zu NO
NO2- + 2 H+ + e- -> NO + H2O
als auch die vier-Elektronen-Reduktion von Sauerstoff zu Wasser:
O2 + 4 H+ + 4 e- -> 2 H2O
Wegen seines Hämgehaltes wird das Enzym auch als Cytochrom cd1 bezeichnet. Die Nitritreduktion ist in denitrifizierenden Bakterien etwa zehnmal effizienter und deswegen als der physiologisch relevante Vorgang anzusehen. Die kupferhaltigen Klasse I - Enzyme werden durch Sauerstoff in einer Wasserstoffperoxid liefernden Reaktion inaktiviert.
Das bei der Nitritreduktion gebildete NO wird von Stickstoffmonoxidreduktasen zu Distickstoffoxid reduziert:
2 NO + NADH + 2 H+ -> N2O + NAD+ + H2O
An dieser Reaktion ist kein weiteres Protein beteiligt, die Elektronen werden direkt zwischen NAD und Häm als prosthetischer Gruppe ausgetauscht. Das Enzym aus dem denitrifizierenden Pilz Fusarium oxysporum konnte sowohl in der freien als in der mit Substrat besetzten Form kristallisiert werden.
Literatur: WG Zumft, Cell Biology and Molecular Basis of Denitrification. Microbiology and Molecular Biology Reviews 61 (1997) 533-616
Translation - English Nitrates react completely to form molecular nitrogen, where nitrites, NO and N2O are stepwise reaction intermediates. For every step, there is a different reductase. In facultative anaerobic bacteria, the nitrate reductase is a transmembrane protein that associates with a nitrate/nitrite antiporter. The nitrite reaction product is delivered to the periplasmic space, where the enzymes for the next two reaction steps are localized (nitrite and NO that escape to the cytoplasm are toxic).
Currently, there are two distinct classes of nitrite reductases known: class I enzymes contain copper as a cofactor, while class II enzymes use a heme group. In the conversion of ammonia to nitrites in the nitrification cycle, there are even hexaheme-containing nitrite reductases. The molecular structures of class I and class II enzymes have been solved.
Class II enzymes catalyze the one electron reduction of nitrite to NO and water:
NO2- + 2 H+ + e- -> NO + H2O
as well as the four electron reduction of oxygen to water:
O2 + 4 H+ + 4 e- -> 2 H2O
Because of its heme content, the class II enzyme is also designated cytochrome cd1. Nitrite reduction is approximately ten times more efficient than oxygen reduction in denitrifying bacteria, and it is therefore regarded as the physiologically relevant reaction. The copper-containing class I enzymes are oxidized, releasing hydrogen peroxide.
NO is a product of nitrite reduction, and is reduced by nitrogen monoxide reductases to N2O:
2 NO + NADH + 2 H+ -> N2O + NAD+ + H2O
No further proteins take part in this reaction; the electrons are directly exchanged between NAD and the prosthetic heme group. The enzyme from denitrifying mushroom Fusarium oxysporum has been crystallized both in the substrate-bound and apo forms.
Literature:
WG Zumft, Cell Biology and Molecular Basis of Denitrification. Microbiology and Molecular Biology Reviews 61 (1997) 533-616
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Experience
Years of experience: 18. Registered at ProZ.com: Jun 2006.
I have a doctorate in biochemistry, and I have two and a half years postdoctoral research experience in an immunology laboratory, specializing in x-ray crystallography for protein structure determination. I have collaborated with biologists, chemists, and an M.D. during the course of my work. I have also published my work. Thus, I have intimate working knowledge of basic science and biomedical research, and professional experience doing technical writing in these and related fields.
My German career began with a year-long exchange program in Austria eleven years ago, where my studies included technical/scientific German language courses. I have also translated nonscientific German for fun. My scientific training means I am careful to produce extremely rigorous and precise translations.
Keywords: Biochemistry PhD, Immunology postdoc, Medical, research, biophysics, protein purification, protein expression, protein chemistry
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