Genetic evidence for role of DPP IV in intestinal hydrolysis and assimilation of prolyl peptides

The functional role of dipeptidyl peptidase IV (DPP IV) in the intestinal hydrolysis and assimilation of prolyl peptides was investigated using Japan F344 rats, which genetically lack this enzyme. USA F344 rats possess normal activity of this enzyme and served as matched controls. Intestinal brush-border membranes from the control rats were able to hydrolyze several proline-containing peptides. The hydrolytic ability of the brush-border membranes from the Japan rats against these peptides was markedly low. The difference in the hydrolytic activities between the two groups of rats was solely due to the absence of DPP IV in the Japan rats. There was no difference in the growth rate between the two groups of rats fed a reference diet whose protein constituents were not rich in proline. When the protein source was changed to gliadin, a proline-rich protein, USA F344 rats maintained their body weight for a 4-wk period on this diet, whereas the Japan rats experienced a significant weight loss under similar cond...