IDENTIFICATION OF URINARY DIPEPTIDASE AS THE RELEASED FORM OF RENAL DIPEPTIDASE

Amphipathic and hydrophilic forms of human renal dipeptidase and urina ry dipeptidase were purified by affinity chromatography using cilastat in, a dipeptidase inhibitor, as the ligand. The sequence analyses of t he 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) an d a single band in sodium dodecyl sulfate-polyacrylamide gel electroph oresis indicate that the enzymes are composed of homotetramers. This i s the most direct evidence that urinary dipeptidase is the released fo rm of renal dipeptidase. In fact, they are the same enzymes.