Human complement 5a (C5a) is an enzymatically generated glycoprotein that belongs to a family of structurally and functionally related proteins known as anaphylatoxins. C5a is a 74 amino acid (aa) peptide that is created by the activity of C5a convertase on the C5 alpha-chain. Human C5a has four alpha-helices plus three intrachain disulfide bonds that create a triple loop structure.