Fusion products containing insoluble proteinaceous tag

In a process for the preparation of a recombinantly expressed fusion product comprising a proteinaceous tag and a soluble protein of interest and the separation of said fusion product from the host cell in which it is expressed comprising the steps of, (1) preparing a vector containing a DNA sequence coding for the protein of interest and the DNA sequence coding for the tag, (2) introducing said vector into a host cell and expressing the fusion product, (3) lysing the host cell with a lysate solution, and (4) separating the fusion product from the host cell lysate solution, the improvement wherein the tag and in turn the fusion product is insoluble in the host cell lysate solution and said fusion product is precipitated from the lysate solution and is substantially separated from host cell proteins by centrifugation or filtration, wherein the protein of interest is (PPAR) peroxisome proliferator-activated receptor and wherein the proteinaceous tag is uricase.