Hydrolysis of bovine and caprine milk fat globules by lipoprotein lipase. Effects of heparin and skim milk on lipase distribution and on lipolysis
Heparin can dissociate lipoprotein lipase from casein micelles, and addition of heparin enhances lipolysis in bovine but not in caprine milk. Heparin shortened the lag-time for binding of lipoprotein lipase to milk fat globules and for lipolysis. Heparin counteracted the inhibitory effects of skim milk on binding of lipase and on lipolysis. Heparin stimulated lipolysis in all bovine milk samples when added before cooling and in spontaneously lipolytic milk samples also when added after cooling. Heparin enhanced lipolysis of isolated milk fat globules. Hence, its effect is not solely due to dissociation of lipoprotein lipase from the casein micelles. Cooling of goat milk caused more marked changes in the distribution of lipase than cooling of bovine milk; the fraction of added /sup 125/I-labeled lipase that bound to cream increased from about 8 to 60%. In addition, caprine skim milk caused less inhibition of lipolysis than bovine skim milk. These observations provide an explanation for the high degree of cold storage lipolysis in goat milk. Heparin had only small effects on the distribution of lipoprotein lipase in caprine milk, which explains why heparin has so little effect on lipolysis in caprine milk. The distribution of /sup 35/S-labeled heparin in bovine milk was studied. In warm milk less than 10% bound to the cream fraction, but when milk was cooled, binding of heparin to cream increased to 45%. These results suggest that there exists in the skim fraction a relatively small amount of a heparin-binding protein, which on cooling of milk adsorbs to the milk fat, or suggests that cooling induces a conformational change in a membrane protein such that its affinity for heparin increases.
- Research Organization:
- Univ. of Norway
- OSTI ID:
- 5341780
- Journal Information:
- J. Dairy Sci.; (United States), Vol. 70:12
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BUTTER FAT
ENZYMATIC HYDROLYSIS
HEPARIN
BIOLOGICAL EFFECTS
LIPASE
ENZYME ACTIVITY
COWS
GOATS
IODINE 125
LABELLED COMPOUNDS
LIPOPROTEINS
SULFUR 35
TRACER TECHNIQUES
AMINES
ANIMALS
ANTICOAGULANTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOHYDRATES
CARBOXYLESTERASES
CATTLE
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DOMESTIC ANIMALS
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
ESTERASES
ESTERS
EVEN-ODD NUCLEI
FATS
HEMATOLOGIC AGENTS
HYDROLASES
HYDROLYSIS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LIPIDS
LYSIS
MAMMALS
MUCOPOLYSACCHARIDES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
POLYSACCHARIDES
PROTEINS
RADIOISOTOPES
RUMINANTS
SACCHARIDES
SOLVOLYSIS
SULFUR ISOTOPES
TRIGLYCERIDES
VERTEBRATES
553005* - Agriculture & Food Technology- Animal Husbandry- (1987-)