Functional characterization of enzymes plays an essential role in one of the major areas of proteomics research: the modelling of sections of the cellular metabolism with a view to being able to model the whole cellular metabolism and the interaction of cells within tissues and organs. With these purposes in mind, the scientific community established a new branch within the life sciences, called systems biology. However, meaningful modelling, by necessity, requires comparable and reliable data from standardized enzyme characterizations. From a short, but detailed, investigation of the BRENDA database, it is shown here that the quality of experimental data of enzymes is insufficient for the needs of theoretical biology. Here we describe the dilemma of modern enzymology which generates functional data from enzymes under nonstandardized experimental conditions followed by suggestions how to remedy this situation by initiating broad discussions within the scientific community and introducing to a new initiative, called STRENDA.