Purification and Properties of Dipeptidyl Peptidase IV from Human Urine

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Abstract
Dipeptidyl peptidase IV (DPP-IV) (EC 3.4.14.5) has been purified from normal human urine using immunoaffinity chromatrography. The purified enzyme was homogeneous as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The molecular mass of urinary DPP-IV was estimated to be 280 kDa by gel filtration. The Km value for the hydrolysis of (Gly-L-Pro)-4-methylcoumaryl-7-amide tosylate was calculated to be 1.25 .+-. 0.25 .times. 10-4 M; the pH optimum and pI were 8.7 and 6.5, respectively. These properties were the same as those of renal DPP-IV. Both renal and this urinary DPP-IV were inhibited by diisopropylfluorophosphate and activated by phospholipid. From these results we suppose that urinary DPP-IV may be derived from the kidney rather than from the blood.