Hoover-Plow J L, Boonmark N, Skocir P, Lawn R, Plow E F
Joseph J. Jacobs Center for Thrombosis and Vascular Biology, Cleveland Clinic Foundation, Ohio 44195, USA.
Arterioscler Thromb Vasc Biol. 1996 May;16(5):656-64. doi: 10.1161/01.atv.16.5.656.
Apo(a), the unique apoprotein of lipoprotein(a) (Lp[a]), can express lysine-binding sites(s) (LBS). However, the LBS activity of Lp(a) is variable, and this heterogeneity may influence its pathogenetic properties. An LBS-Lp(a) immunoassay has been developed to quantitatively assess the LBS function of Lp(a). Lp(a) within a sample is captured with an immobilized monoclonal antibody specific for apo(a), and the captured Lp(a) is reacted with an antibody specific for functional LBS. The binding of this LBS-specific antibody is then quantified by using an alkaline phosphatase-conjugated disclosing antibody. The critical LBS-specific antibody was raised to kringle 4 of plasminogen. When applied to plasma samples, the LBS activity of Lp(a) ranged from 0% to 100% of an isolated reference Lp(a); the signal corresponded to the percent retention of Lp(a) on a lysine-Sepharose but did not correlate well with total Lp(a) levels in plasma. Mutation of residues in the putative LBS in the carboxy-terminal kringle 4 repeat (K4-37) in an eight-kringle apo(a) construct resulted in marked but not complete loss of activity in the LBS-Lp(a) immunoassay. These data suggest that this kringle is the major but not the sole source of LBS activity in apo(a). The LBS-Lp(a) immunoassay should prove to be a useful tool in establishing the role of the LBS in the pathogenicity of Lp(a).
载脂蛋白(a) [Apo(a)]是脂蛋白(a) [Lp(a)]的独特载脂蛋白，能够表达赖氨酸结合位点（LBS）。然而，Lp(a)的LBS活性存在差异，这种异质性可能会影响其致病特性。一种用于定量评估Lp(a)的LBS功能的LBS-Lp(a)免疫测定法已经开发出来。样品中的Lp(a)用针对Apo(a)的固定化单克隆抗体捕获，捕获的Lp(a)与针对功能性LBS的抗体反应。然后使用碱性磷酸酶偶联的显色抗体对这种LBS特异性抗体的结合进行定量。关键的LBS特异性抗体是针对纤溶酶原的kringle 4产生的。当应用于血浆样本时，Lp(a)的LBS活性范围为分离的参考Lp(a)的0%至100%；该信号对应于Lp(a)在赖氨酸-琼脂糖上的保留百分比，但与血浆中总Lp(a)水平的相关性不佳。在一个八kringle的Apo(a)构建体中，羧基末端kringle 4重复序列（K4-37）中假定LBS的残基发生突变，导致LBS-Lp(a)免疫测定中的活性显著但未完全丧失。这些数据表明，这个kringle是Apo(a)中LBS活性的主要但不是唯一来源。LBS-Lp(a)免疫测定法应被证明是确定LBS在L p(a)致病性中作用的有用工具。
