<unk> (a)<unk> (a) consists of an LDL-like particle and the specific apolipoprotein(a), which is bound covalently to the apoB contained in the outer shell of the particle.<unk> (a) plasma concentrations are highly heritable and mainly controlled by the<unk> A gene located on chromosome 6q26-27. Apo(a) proteins vary in size due to a size polymorphism KIV-2 VNTR, which is caused by a variable number of kringle IV repeats in the<unk> A gene. This size variation at the gene level is expressed on the protein level as well, resulting in apo(a) proteins with 10 to more than 50 kringle IV repeats (each of the variable kringle IV consists of 114 amino acids). These variable apo(a) sizes are known as "apo(a) isoforms". There is a general inverse correlation between the size of the apo(a) isoform and the<unk> (a) plasma concentration. One theory explaining this correlation involves different rates of protein synthesis. Specifically, the larger the isoform, the more apo(a) precursor protein accumulates intracellularly in the endoplasmic reticulum.<unk> (a) is not fully synthesised until the precursor protein is released from the cell, so the slower rate of production for the larger isoforms limits the plasma concentration. Populations<unk> (a) concentrations can vary by more than one thousand between individuals, from 200 mg/dL. This range of concentrations is observed in all populations studied by scientists so far. The mean and median concentrations differ among world populations. Most prominently, there is a two- to threefold higher mean<unk> (a) plasma concentration in populations of African descent compared to Asian, Oceanic, or European populations. The general inverse correlation between apo(a) isoform size and<unk> (a) plasma concentration is observed in all populations. However, it was also discovered that mean<unk> (a) associated with certain apo(a) isoforms varies between populations. In addition to size effects, mutations in the<unk> A promoter may also lead to a decreased apo(a) production.
Lipoprotein
Bile acid
Blood protein
Apolipoprotein
Cholesterol
High-density lipoprotein
Plasma-lyte
Hemoglobin