A proteoform (synonym protein species) is defined as smallest unit of the proteome (Jungblut 2008, Schlüter 2009). From a specific gene usually many proteoforms are generated (Aebersold 2018). It is estimated that approximately 1 billion proteoforms are appearing during the life-time of a human (Kelleher 2012). Proteoforms coded by the same gene can be both very similar, differing in a few atoms only but also very different. Most important for their biology is that their composition of atoms and their structure determines their function and activity. Peptides, such as e.g. angiotensin peptides, are also proteoforms. Since peptides can be identified and synthesized more easily than large proteoforms, more detailed knowledge about the functions and activities of proteoforms being peptides is available. However, even peptidic proteoforms are not well and systematically represented in knowledgebases. This problem will be demonstrated on the example of angiotensinogen proteoforms (Hildebrand, 2013). The new Human Proteoform Atlas (HprfA) will overcome this current problem since it is integrating experimentally derived data describing the exact composition of proteoforms in relationship to their functions and activities (Hollas 2022).