Apolipoprotein E Polymorphism in Cerebrovascular & Coronary Heart Diseases (Report)
Introduction The human apolipoprotein E (apo E) is a serum glycoprotein consisting of 299 amino acids found in circulating chylomicrons, chylomicron remnants, very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL) and high-density lipoproteins (HDL) (1). The apolipoprotein E gene (APO E) is located at chromosome 19q 13.2 and consists of four exons and three introns spanning 3,597 nucleotides (1,2). ApoE is a 35 kilodalton (kD) glycosylated protein with multiple biological properties (3). It is produced primarily in the liver, but other organs and tissues also synthesize apo E, including brain, spleen, kidneys, gonads, adrenals and macrophages. The structural gene locus for plasma apo E is polymorphic having three common alleles, designated as [epsilon]2, [epsilon]3 and [epsilon]4 which code for E2, E3 and E4 proteins, respectively. Consequently three homozygous (E2/E2, E3/E3, E4/ E4) and three heterozygous (E3/E2, E4/E2 and E4/E3) phenotypes are found in the general population4. The product of the three alleles differ in such properties as its affinity for binding to apo E and low-density lipoprotein receptors (LDL-R), and its affinity for lipoprotein particles (5).