Influences of apolipoprotein E on soluble and heparin-immobilized hepatic lipase
The effect of human apolipoprotein E (apoE), either alone or in combination with apoC, on the lipolysis of a radiolabeled triglyceride emulsion was studied with hepatic lipase in solution and immobilized on heparin-Sepharose. The soluble hepatic lipase was inhibited, whereas the heparin-immobilized lipase was stimulated by apoE. This stimulation was attenuated by combining apoE with either apoC-II or C-III. The heparin-immobilized lipase demonstrated much less lipolysis of the zwitterionic phosphatidylcholine-stabilized triglyceride emulsion than did the soluble enzyme. This difference was less when the emulsion was stabilized by a nonionic detergent. apoE inhibited lipase activity when assayed under conditions (0.4 M NaCl) of bound enzyme and unbound substrate. Increasing the emulsion apoE content beyond optimum inhibited lipolysis by the immobilized enzyme. Kinetic analysis of phosphatidylcholine-stabilized triglyceride emulsions revealed a significant decrease in immobilized enzyme K/sub m/ and an increase in V/sub max/ when the emulsion was supplemented with apoE. Distributing the immobilized lipase in clustered aggregates produced more lipolysis than when the same enzyme content was uniformly bound.
- Research Organization:
- Duke Univ. Medical Center, Durham, NC (USA)
- OSTI ID:
- 7039889
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 252:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
APOLIPOPROTEINS
BIOCHEMISTRY
TRIGLYCERIDES
BIOCHEMICAL REACTION KINETICS
LYSIS
CARBON 14 COMPOUNDS
DOSE-RESPONSE RELATIONSHIPS
ELECTROPHORESIS
EMULSIONS
ENZYME ACTIVITY
LIPASE
LIVER
PURIFICATION
TRITIUM COMPOUNDS
BODY
CARBOXYLESTERASES
CHEMISTRY
COLLOIDS
DIGESTIVE SYSTEM
DISPERSIONS
ENZYMES
ESTERASES
ESTERS
GLANDS
HYDROLASES
KINETICS
LABELLED COMPOUNDS
LIPIDS
LIPOPROTEINS
ORGANIC COMPOUNDS
ORGANS
PROTEINS
REACTION KINETICS
550201* - Biochemistry- Tracer Techniques