Enzyme mimicry by the antiidiotypic antibody approach

Enzyme mimicry by the antiidiotypic antibody approach

^*Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Mikluho-Maklaya Street, Moscow 117871, Russia; ^‡Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, Moscow 117324, Russia; ^§Center for Chemical Immunology and Therapeutics, Department of Pathology and Lab Medicine, University of Texas, Houston Medical School, 6431 Fannin, Houston, TX 77030; and ^†Unité 6022 associée Centre National de la Recherche Scientifique, Université de Technologie de Compiègne, BP 20529–60205 Compiègne Cedex, France

Communicated by Jean-Marie P. Lehn, Universite Louis Pasteur, Strasbourg, France (received for review March 7, 2000)

Abstract

The concept of “internal image” of antiidiotypic antibodies has provided the basis for eliciting catalytic antibodies. A monoclonal IgM 9A8 that was obtained as an antiidiotype to AE-2 mAb, a known inhibitor of acetylcholinesterase, displayed esterolytic activity. Study of recombinant Fab fragments and separate light and heavy chains of 9A8 confirmed that the antibody variable domain encodes the catalytic function, whereas neither part of the primary sequence of the Fab exhibited homology with the enzyme. The specific modification of the 9A8 variable domain by an active site-directed covalent inhibitor revealed the presence of an active site Ser residue. A three-dimensional modeling suggests the existence of a functional catalytic dyad Ser-His. Comparison of active sites of 9A8 and 17E8 esterolytic abzyme raised against transition-state analog revealed structural similarity although both antibodies were elicited by two different approaches.

Footnotes

↵ ¶ A.G.G. and A.F. contributed equally to this work.
↵ ‖ To whom reprint requests should be addressed. E-mail: Alain.Friboulet{at}utc.fr.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. AF253060 and AF253061).
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.200360497.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.200360497
Abbreviations:

TSA,

transition-state analog;

AcChoE,

acetylcholinesterase;

BtChoEase,

butyrylcholinesterase;

CDR,

complementarity determining regions;

VH,

VL, the variable domains of the heavy (H) and light (L) chains;

DTNB,

5,5′-dithiobis(2-nitrobenzoic acid)