g. causing conflicts between data in text and tables, usage of standard formats and names, and defined usage of referenced values and experimental methods. None of the authors

have any conflict of interest. The SABIO-RK project is financed by the Klaus Tschira Foundation (http://www.klaus-tschira-stiftung.de/), the German Federal Ministry of Education and Research (http://www.bmbf.de/) through Virtual Liver and SysMO-LAB (Systems Biology of Microorganisms), and the DFG LIS (http://www.dfg.de/) as part of the project Integrierte Immunoblot Umgebung. “
“Enzyme assays are performed to serve two different purposes: (i) to identify a special enzyme, to prove its presence or absence in a distinct specimen, like an organism or a tissue and (ii) to determine the amount of the enzyme in the sample. While for the first, Birinapant cost the qualitative approach, a clear positive or negative result is sufficient, the second, the quantitative approach must deliver Vemurafenib cost data as exact as possible. A great advantage of enzymes is that they can

be identified by their catalysed reactions, in contrast to the other components of the cell, like functional proteins or nucleic acids, which must be determined by direct detection. During the enzyme reaction product accumulates in amounts exceeding by far the intrinsic enzyme concentration. However, the conclusion from the product formed back to the amount of enzyme in the sample comprises various difficulties and pitfalls. Procedures for enzyme assays are documented or cited in various standard books (Methods in Enzymology; Advances in Enzymology

and Related Areas of Molecular Biology; Methods of Enzymatic Analysis (Bergmeyer, 1983); Springer Handbook of Enzymes (Schomburg, 2009); Practical Enzymology (Bisswanger, 2011) and databases (ExPASy database, and Brenda database,), but even accurate observance learn more gives no guarantee of an unequivocal outcome. The same assays performed independently under obviously identical conditions may yield quite different results. In fact, the enzyme activity depends on manifold factors and general understanding of the particular features of enzymes is required, which cannot be described in all details in protocols for special enzyme assays. The most important aspects to be considered for enzyme assays are the subject of this article. It was the merit of Leonor Michaelis and Maud Menten (Michaelis and Menten, 1913) to realize that the enzyme activity depends decisively on defined conditions with respect to temperature, pH, nature and strength of ions and enzyme assays can reliably only be compared, if such conditions are strictly regarded. Considering these conditions, it may appear a simple task to define general rules valid for all enzyme assays, but such an endeavour will fail because of the great diversity of enzymes and their features.