Generation of Efficient Tailormade Biocatalysts (Catalytic Antibodies) by Heterologous Immuniztion

从1986年催化抗体的第一次报道开始，已经产生了各种各样的抗体，并发现它们催化从环周反应到酰胺键水解的化学转化。它们中的大多数是由过渡态类似物的免疫引起的。然而，不幸的是，这些抗体的催化活性并不充分，并且由抗体催化的大多数反应是酯水解。我们设计了一种称为异源免疫的新策略，其中动物连续用两种不同但结构相关的半抗原免疫。在异源免疫后，宿主可以对第二半抗原交叉反应性地应答，并产生对第一和第二半抗原都具有亲和力的抗体。当两个半抗原分别含有正电荷或负电荷并结合在过渡态类似物的结构中时，该半抗原对的异源免疫提供了在抗体结合位点同时产生酸性和碱性催化残基的机会。膦酸半抗原的两次连续免疫，然后用胺半抗原加强，诱导催化抗体，与从单一半抗原免疫获得的那些相比，具有更高的速率加速。这些催化抗体中的大多数具有交叉反应性的半抗原，膦酸和胺半抗原，和催化活性被有效地抑制两种半抗原。这些结果表明，异源免疫策略提供了一种潜在的手段，引入多个催化残基到抗体结合位点。

From the first report of catalytic antibodies in 1986, a variety of the antibodies has been generated and found to catalyze chemical transformations from peri-cyclic reactions to amido-bond hydrolyses. Most of them are elicited by immunization of transition-state analogs. However, unfortunately, the catalytic activities are not sufficient and the most of the reactions catalyzed by the antibodies are esterolytic hydrolysise. We have devised a new strategy called heterologous immunization wherein an animal is immunized in succession with two different but structurally related haptens. Upon heterologous immunization, the host may respond crossreactively to the secondary hapten and produce antibodies which have affinity for both of the primary and secondary hapten. When two haptens individually contain either a positive or negative charge incorporated in the structure of a transition-state analog, the heterologous immunization of this hapten pair provides an opportunity to simultaneously generate an acidic and an basic catalytic residue in an antibody combining site. Two successive immunization of phoshonate hapten, followed by a boost with amine hapten, induced catalytic antibodies with a higher rate acceleration compared with those obtained from immunization of a single hapten. The majority of these catalytic antibodies possessed cross-reactivities to both haptens, phoshonate and amine haptens, and the catalytic activities were effectively inhibited by both haptens. These results imply that the heterologous immunization strategy offers a potential means of introducing multiple catalytic residues into antibody combining site.