The multi-disciplinary approaches which are now typical of research in the natural and life sciences use a combination of modern experimental techniques which have led to an increased accuracy in the measurements of enzyme structures and activities. Modern analysis methods often result in the generation of huge amounts of data and large data sets, which are subsequently published in electronic data repositories and in written papers. However, data in both the literature and in databases suffer from the fact that they are often non-comparable due to incomplete and imprecise descriptions of materials and methods. Furthermore, if the experimental conditions are not fully and accurately stated, the values of the functional data of enzyme activities are of little use for, in particular, systems biology applications.Further problems occur even when the data are well reported; they will have often been collected under quite disparate conditions so that researchers are faced with the problem of the range of method-specific enzyme data. This is often an issue when data move between researchers whose data are supplied by laboratories that use different methods, and can, in the worst case, lead to misinterpretation of laboratory findings. The topics of the Proceedings of the 5th Symposium on ESCEC range from describing how the modification of enzyme structures affects the kinetics of enzyme reactions to discussing new results, approaches and methodologies for establishing physiological ties between sequence, structure and kinetics and modeled networks of collaborative enzymes. The overall topic - standard representation of enzyme data - is still considered and discussed in precise detail.