Non-canonical peptides (NCPs) are a class of peptides generated from regions previously thought of as non-coding, such as introns, 5' untranslated regions (UTRs), 3' UTRs, and intergenic regions. In recent years, the significance and diverse functions of NCPs have come to light, yet a systematic and comprehensive NCP database remains absent. Here, we developed NCPbook (https://ncp.wiki/ncpbook/), a database of evidence-supported NCPs, which aims to provide a resource for efficient exploration, analysis, and manipulation of NCPs. NCPbook incorporates data from diverse public databases and scientific literature. The current version of NCPbook includes 180,676 NCPs across 29 different species, evidenced by mass spectrometry (MS), ribosome profiling (Ribo-seq), or molecular experiments (ME). These NCPs are distributed across kingdoms, comprising 123,408 from 14 plant species, 56,999 from seven animal species, and 269 from eight microbial species. Furthermore, NCPbook encompasses 9,166 functionally characterized NCPs playing important roles in immunity, stress resistance, growth, and development. Equipped with a user-friendly interface, NCPbook allows users to search, browse, visualize, and retrieve data, making it an indispensable platform for researching NCPs in various plant, animal, and microbial species.
