The objective of the Springer Handbook of Enzymes is to provide in concise form data on enzymes sufficiently well characterized. Data sheets are arranged in their EC-Number sequence. Each volume comprises one enzyme class, sometimes the enzyme classes have to be divided into several volumes. Considerable progress has been made in enzymology since the publication of the first edition (published as "Enzyme Handbook"): many enzymes are newly classified or reclassified. In the 2nd edition each entry is correlated with references and one or more source organisms. New datafields are created: "application" and "engineering" (for the properties of enzymes where the sequence has been changed). Altogether the amount of data has doubled so that the 2nd edition will consist of 39 volumes plus synonym index. This collection is an indispensable source of information for researchers in biochemistry, biotechnology, organic and analytical chemistry, and food sciences.