Identification of urinary dipeptidase as the released form of renal dipeptidase

Amphipathic and hydrophilic forms of human renal dipeptidase and urinary dipeptidase were purified by affinity chromatography using cilastatin, a dipeptidase inhibitor, as the ligand. The sequence analyses of the first ten amino acids of renal and urinary dipeptidases were shown to be identical, and they are Asp-Phe-Phe-Arg-Asp-Glu-Ala-Glu-Arg-Ile. Unambiguous results of amino acid sequencing, the molecular weight of native protein (190 kD), the molecular weight of subunit (47.7 kD) and a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicate that the enzymes are composed of homotetramers. This is the most direct evidence that urinary dipeptidase is the released form of renal dipeptidase. In fact, they are the same enzymes.