EVIDENCE THAT LP[A] CONTAINS ONE MOLECULE OF APO[A] AND ONE MOLECULE OF APO-B - EVALUATION OF AMINO-ACID-ANALYSIS DATA

Amino acid analysis was performed on four Lp[a] preparations to evalua te whether or nor the amino acid data was consistent with Lp[a] contai ning one molecule of apolipoprotein[a] [apo(a)] linked to one molecule of apoB-100. Amino acid analysis was carried our in duplicate on a Be ckman model 121 amino acid analyzer. Apo[a] size was determined by a h igh-resolution agarose gel electrophoretic method that provides an est imate of apo[a] kringle 4 repeats. When Lp[a] was assumed to contain o ne apo[a] and one apoB molecule per particle, the average absolute bia s between the expected molar percentage of each amino acid, as based o n the known sequence of apo[a] and apoB, and the obtained molar percen tage ranged from 2 to 3.5%. In contrast, by assuming two molecules of apo[a] and one of apoB per Lp[a] particle, the bias between the expect ed and ob served molar percentage ranged from 8.5% to 10%, and by assu ming one apo[a] and two apoB the bins ranged from 8.8% to 11.4%. Compa rison of Lp[a] concentrations, calculated from six stable amino acids and the Lp[a] composition predicted from the known sequence, was in ex cellent agreement (bias ranging from 0.3% to 0.9%) with the Lp[a] conc entration calculated from the sum of the amino acid concentrations, wh en Lp[a] was assumed to contain one molecule of apo[a] and one molecul e of apoB. However, there was poor agreement (7.4% to 8.4% bias) when it was assumed that Lp[a] contains two molecules of apo[a] and one mol ecule of apoB. These results indicate that the evaluated Lp[a] prepara tions contain one apo[a] per Lp[a] particle. Evaluation of amino acid analysis data provides a relatively simple approach to determine the m olar ratio of apoB to apo[a] in Lp[a] and provides evidence that Lp[a] contains one molecule of apo[a] and one molecule of apoB.