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uni'wissen 02-2012 ENG

They are small, their names sound complicat- ed – and they are important for the environ- ment: the enzymes nitrogenase and nitrous-oxide reductase. In nature they occur in highly specialized microorganisms. Nitrogenase is used to convert nitrogen (N2) into a fixed form, making it available for plants whose growth is dependent on N2. Nitrogen is one of the funda- mental building blocks of life and accounts for almost 80 percent of the air we breathe. On ac- count of its stability, however, the gas molecule is very difficult to cleave through chemical means and is thus a scarce resource in industri- al agriculture. Farmers therefore use synthetic nitrogen fertilizer to support the growth of their crops. When produced using the so-called Haber–Bosch process, synthetic nitrogen fertil- izer uses up roughly one percent of all globally produced energy at current production volumes. The enzyme nitrous-oxide reductase, on the other hand, cleaves the environmentally harmful gas nitrous oxide (N2O), also known as laughing gas, which is created among other things by soil bacteria during the decomposition of nitroge- nous fertilizer – a process in which large amounts of N2O are released from fertilized crop land. N2O contributes to the depletion of the ozone layer and to the greenhouse effect and is probably the most critical gas for the fate of the climate in the 21st century. In addition, it also re- mains intact in the atmosphere for 120 years. Since natural nitrogen is not available in suffi- cient amounts, farmers use more industrial fertil- izer for their crops, thus releasing even more N2O. Prof. Dr. Oliver Einsle, a biochemist at the University of Freiburg, is tackling this environ- mental problem in his research: He is studying the enzymes nitrogenase and nitrous-oxide re- ductase in order to find a natural alternative to synthetic fertilizer on the one hand and to enable the decomposition of environmentally harmful compounds on the other. “That would be a fun- damental step forward,” says the researcher. “We first need to reach a complete understanding of the basic properties and functions of the enzymes, even if this is a time-consuming endeavor” 17