Abstract: The present invention provides a method for the detection of an enzyme E1 in a liquid sample comprising the steps of: a) providing a complex (Sa-Sb-M), wherein (Sa-Sb) is a substrate S of E1 cleavable into Sa and Sb by E1, and M is a marker linked to Sb, b) incubating the sample with the complex under conditions enabling the cleavage of S into Sa and Sb by E1, c) separating non-cleaved complex (Sa-Sb-M) from the sample, and d) measuring M in the sample. Furthermore, the present invention further provides kits and devices for the detection of an enzyme E1.