Dipeptidase deficiency and malabsorption of glycylglycine in disease states.

The activities of jejunal mucosal peptide hydrolases for glycylglycine, glycyl-L-leucine and L-leucylglycine, were assayed in 37 patients. Eight patients, four of whom had Crohn's disease, were found to have a marked reduction in the activity of glycylglycine dipeptidase and, to a lesser extent, of the other two hydrolases. Although absorption of glycine in the two groups was similar, there was malabsorption of glycylglycine in the patients with reduced dipeptidases as shown by a flat absorption curve. The importance of peptide hydrolases of small-intestinal mucosa in the final digestion of proteins, and the implications of peptidase deficiency in disease states is discussed. It is concluded that significant peptidase deficiency may occur even when the mucosa is otherwise histologically completely normal, similar to some states of disaccharidase deficiency described in recent years.