Enzymatic properties of active form of human apolipoprotein (a).
Lipoproteins (d = 1.05-1.12 g/ml) were obtained from pooled serum by density gradient ultracentrifugation and used as a source for isolation of apolipoprotein (a) (apo(a]. It was found that both these lipoproteins and purified apo(a) possess negligible amidolytic and proteolytic activity. After preincubation of lipoproteins and apo(a) with collagen-Sepharose, the increase in enzymatic activity was observed. The activation of purified apo(a) also occurred upon its storage in the cold. After two week storage at 7 degrees C, the amidase activity, as measured by splitting of the substrate D-Pro-Phe-Arg-pNA, was increased from 0.009 U/mg to 0.85 U/mg. The amidase activity was completely inhibited by phenylmethylsulfonyl fluoride (10(-3) M) and by soybean trypsin inhibitor (10(-5) M); it was not inhibited by aprotinin (10(-6) M). Activated apo(a) did not split azocasein but converted plasma prekallikrein to kallikrein and degraded apolipoprotein B-100.
Institute of Biological and Medical Chemistry, USSR Academy of Medical Sciences, Moscow.
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Chulkova
D001053:Apolipoproteins / Q000097:blood* / Q000302:isolation & purification; D053241:Apoprotein(a); D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007610:Kallikreins / Q000378:metabolism*; D007700:Kinetics; D017270:Lipoprotein(a); D008075:Lipoproteins, HDL / Q000097:blood / Q000302:isolation & purification; D008077:Lipoproteins, LDL / Q000097:blood / Q000302:isolation & purification
D001053:Apolipoproteins; D017270:Lipoprotein(a); D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D053241:Apoprotein(a); D007610:Kallikreins