The CPLM database was developed in a user-friendly manner, while browse and search options were provided for accessing the information. Because the proteins and sites could be classified according to the PLM types and species, two browse options including ‘Browse by types’ and ‘Browse by species’ were developed in the database (Figure 2). For convenience, only 12 major species were listed for browsing, while all the other organisms were denoted as ‘Others’. Here, we use lysine acetylation substrates from Homo sapiens as an example to present the usage of the browse options in CPLM. In the option of ‘Browse by types’, 12 simplified molecular structures of ligands conjugated to lysine residues during modification were employed to represent the 12 types of PLMs (Figure 2A). By clicking on the ‘Acetylation’ button, a brief introduction of protein lysine acetylation and the protein number distribution of acetylated proteins in 12 major organisms and other species were showed (Figure 2A). Then the acetylation substrates in H. sapiens could be listed through clicking on the ‘Homo sapiens’ link (Figure 2B). In the option of ‘Browse by species’, the 12 major organisms were organized as animals, bacteria, fungi and plants. Users could click on the ‘H. sapiens’ button to view the protein number distribution of different PLM substrates in H. sapiens (Figure 2C), and then click on the link of ‘Acetylation’ to view the list of acetylated substrates in H. sapiens (Figure 2B). The detailed information for any specified protein could be accessed through the links in the list (Figure 2D).