Apolipoprotein E Activation and Phosphatidylcholine Substrate Requirements of Lecithin Cholesterol Acyl Transferase

The apolipoprotein activation of lecithin cholesterol acyl transferase (LCAT) by human apolipoprotein E (apo E) was investigated by incorporating apo E into discoidal complexes of egg phosphatidylcholine (egg-PC) and cholesterol by the cholate dialysis method. These complexes were systematically compared to apo A-I complexes synthesized under the same reaction conditions. Apo E was found to be 18% as effective as apo A-I in activating purified human LCAT. Concentration and temperature-dependence experiments on the velocity of the lecithin cholesterol acyl transferase reaction revealed differences in apparent K(,m) values and small differences in apparent V(,max) with very similar activation energies (18-20 kcal/mol). These observations suggest that differences in LCAT activation by apo A-I and apo E are primarily a result in different affinities of the enzyme for the particles. Addition of free apo A-I to apo E complexes resulted in the exchange of bound for free apolipoprotein causing an increase in the reactivity of the enzyme when the unbound apolipoprotein was removed by ultracentrifugation and reisolated complexes were assayed.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biochemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Zorich, Nora Lee

• Chemistry, Biochemistry

Identifier

(UMI)AAI8711909

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70563