The application of alcohol, amino acid, and amine oxidases for the enantioselective oxidation of C-O and C-N bonds, is studied. Dioxygen is a mild oxidant, and coupled with the fact that the reactions takes place at room temperature and pH 7-8, these transformations are to be considered as green and environmentally friendly. Enzymes are inherently selective in the reactions that they catalyze and can often direct the oxidation to one particular part of the molecule. the oxidation of C-N bonds leads to formation of imines and thus constitutes activation of C-H bonds α to an amine, a process that is both synthetically difficult to achieve and at the same time highly useful. Suitable high-throughput screening methods are developed that allow investigation of the relationship between sequence and function.