Biochemical study of dipeptidylpeptidase-4 from normal human serum

الملخص EN

The research includes partial purification of dipeptidylpeptidase-4 (DPP-4) from serum of normal person aging 14 years in Mosul city.

Gel filtration of dialysate precipitate produced by 50% ammonium sulphate saturation has given two major proteinous components.

One of them ( peak A) possesses a high DPP-4 activity using sephedex G-100.

The apparent molecular weight of the isolated DPP-4 was 176.6 KD.

High performance liquid chromatography HPLC revealed a single peak A' at retention time 5.829 min by application the top of peak A which was isolated from gel filtration.

Maximum activity of DPP-4 was obtained using 0.1 M Tris-HCl buffer at pH 8, 40°C, 4 mM of gly-pro-p-nitroanilide hydrochloride as a substrate.

The concentration 0.35 mg/ml partially purified DPP-4 was used for next experiments.

Maximum velocity (Vmax) was 50 μM according to Line Weaver-Burk plot while Michaelis–Menten constant (Km) was 0.5 mM.

Mercuric chloride and strontium chloride hexahydrate at 5 mM revealed maximum inhibitory effect of DPP4 activity by 30.2% and 42.9% respectively