The 15 base pairs in exon 1 encoding enterostatin, a pentapeptide (APGPR) produced from cleavage of the pro-colipase peptide, were removed. A floxed neo cassette was also inserted into intron 1 and subsequently removed by cre mediated recombination. Normal expression of a slightly smaller colipase protein was confirmed by western blot analysis on pancreas extracts. Enzymatic assay confirmed normal colipase activity. (J:159587)