Characterization of metalloelastase-like activity from the plasma of a patient with Tangier disease

An enzymatic activity with releases p-nitroaniline from 3-carboxypropionyl-trialanine p-nitroanilide (Suc[Ala]3NA) was characterized in blood plasma of patients with Tangier disease. This activity results from the sequential action of a metalloendopeptidase (MP) and an aminopeptidase (AP). These proteases were purified 134- (MP) and 82-fold (AP) from low density and very low density lipoproteins (LDL and VLDL) depleted Tangier plasma by DEAE-Trisacryl chromatography and gel filtration. MP and AP could be separated by polyacrylamide gel electrophoresis. MP shares some analogy with neutral endopeptidase (membrane metalloendopeptidase, EC 3.4.24.11) and is able to degrade human plasma fibronectin (mainly to fragments of 185, 168 and 128 kDa) as evidenced on Western blots. It cannot hydrolyse 3H-labelled insoluble elastin and apolipoprotein AII, but did cleave a dinitrophenyl-octapeptide as well as apolipoprotein AI to 25-kDa and 24-kDa fragments formed sequentially. It may therefore be partially responsible for the in vivo degradation of apoAI observed in Tangier disease.