597548 Disclosed is a method of concentrating a composition comprising porphobilinogen deaminase and/or functionally equivalent parts and analogues hereof comprising: a) centrifugation and/or filtration of a composition comprising porphobilinogen deaminase b) concentrating the supernatant or filtrate, respectively, obtained from step a), c) obtaining from the concentrated supernatant or filtrate of step b) an isotonic solution comprising porphobilinogen deaminase, d) formulating the isotonic solution for injection, and wherein the functionally equivalent part or analogue thereof exerts substantially the same enzymatic activity as the full-length enzyme.
