 In this tutorial, we will learn how to search for the enzymes corresponding to a rear reaction in the Uniprot knowledge base. As an example, we will take the protein encoded by the gene DXMT of the Robusta coffee plant, which can be found in the Uniprot KB Swissport record with the accession number A4GE70. In the simple rear search box, we can type Uniprot colon A4GE70 and click on search. We could also have done the same query by using the advanced search. To do so, we click on advanced search, then on all, select Uniprot KBAC, type the accession number and click on search. The protein from Robusta coffee corresponding to our record catalyzes three different biochemical reactions all related to the biosynthesis of caffeine. We can click on one of the reaction identifiers to go to the page presenting detailed information about the reaction. In addition to the graphical representation of the reaction and many other details, there is a link to the corresponding enzymes, which leads to the Uniprot website. If we want to go to this information more directly, straight from the rear search result table, there is a column in the result view that shows the number of Uniprot KB protein records linked with each rear reaction. We can obtain the protein records associated with a given reaction simply by clicking on the corresponding link in that column. This is the search result table on the Uniprot website with the different proteins related to our rear reactions. Our selected reaction is associated with eight Uniprot KB records describing the products of different genes from six different organisms, including the protein record corresponding to the DXMT gene from Robusta coffee. The query box up here is filled with the corresponding reaction query. It can be edited if we want to further explore these results and the richness of the Uniprot KB annotations. If we go back to our reaction table, we can also select one or more rear reactions and click on the red find enzymes button to obtain a similar result on the Uniprot website as before but for more than one reaction. It is important to note that not all rear reactions are linked to a protein in Uniprot KB. Not all organisms have fully sequenced genomes and the set of protein sequences in Uniprot KB is therefore not necessarily complete for these or the sequence could be available but has been labeled as uncharacterized by the genome consortium. Making the links between protein sequences and enzymatic activity is an ongoing and collaborative process between rear and Uniprot curators. About two-thirds of all reactions in rear are linked to one or more protein records in Uniprot KB but this number as well as all other numbers shown in this tutorial will change regularly depending on the evolution of biological knowledge and on biocuration efforts. Never hesitate to contact us and to look at our help pages and other videos. Thanks for your attention.