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), Journal Name: Am. J. Physiol.; (United States) Vol. 252:6; ISSN AJPHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
APOLIPOPROTEINS
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
BODY
CARBON 14 COMPOUNDS
CARBOXYLESTERASES
CHEMISTRY
COLLOIDS
DIGESTIVE SYSTEM
DISPERSIONS
DOSE-RESPONSE RELATIONSHIPS
ELECTROPHORESIS
EMULSIONS
ENZYME ACTIVITY
ENZYMES
ESTERASES
ESTERS
GLANDS
HYDROLASES
KINETICS
LABELLED COMPOUNDS
LIPASE
LIPIDS
LIPOPROTEINS
LIVER
LYSIS
ORGANIC COMPOUNDS
ORGANS
PROTEINS
PURIFICATION
REACTION KINETICS
TRIGLYCERIDES
TRITIUM COMPOUNDS