Monoclonal antibodies to bovine milk lipoprotein lipase. Evidence for proteolytic degradation of the native enzyme.
Lipoprotein lipase was purified from bovine skim milk by chromatography on heparin-Sepharose. Polyacrylamide gel electrophoresis showed a single protein with an apparent molecular weight of 55,000 in the trailing edge of the elution profile; fractions in the leading edge contained additional proteins with molecular weights of 36,000 and 18,000-22,000. Nine monoclonal antibodies were prepared against the 55,000-dalton protein. By immunoblotting, we show that the Mr = 18,000-22,000 components share common antigen determinants with the 55,000-dalton protein, suggesting that they represent proteolytic degradation products. Incubation of partially purified lipoprotein lipase for 24 h at 37 degrees C results in breakdown of the 55,000-dalton protein with concomitant enrichment in lower Mr components; the proteolytic activity is prevented by incubating the milk with phenylmethane, sulfonyl fluoride prior to chromatography on heparin-Sepharose. This study shows the presence of milk proteases which co-purify and degrade lipoprotein lipase. We suggest that this degradation could account for part of the known instability of the enzyme.
Socorro
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Jackson
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D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D002417:Cattle; D000939:Epitopes / Q000276:immunology; D007120:Immunochemistry; D008071:Lipoprotein Lipase / Q000276:immunology* / Q000302:isolation & purification; D008892:Milk / Q000201:enzymology*; D008970:Molecular Weight; D010446:Peptide Fragments / Q000276:immunology / Q000302:isolation & purification; D010447:Peptide Hydrolases
D000911:Antibodies, Monoclonal; D000939:Epitopes; D010446:Peptide Fragments; D008071:Lipoprotein Lipase; D010447:Peptide Hydrolases