[Action of aortic cathepsin D on serum low-density lipoproteins]

Action of aortic cathepsin D on low density lipoproteins /LDL/ from human serum was studied by means of analytical ultracentrifugation. Cathepsin D intensively hydrolysed LDL, leading to decrease in the sedimentation coefficients of the product formed. The product of degradation of LDL possessing a sedimentation coefficient of 4.5 S /in 0,04 M KBr; 0,042 M NaCl, 2 mM EDTA, 6 mM Tris, pH 7.3 /contained apparently the minimal amount of proteins, which could still maintain the stability of partially hydrolysed LDL. When the degree of hydrolysis reached 40%, a heterogenous mixure, containing the flotating and slowly sedimenting products, was formed. These products gradually lost their solubility. The data obtained suggest that the insoluble products of the proteolysis may be formed in aortic wall some disorders of the lipoprotein metabolism.