Catalytic antibody light chain capable of cleaving a chemokine receptor CCR‐5 peptide with a high reaction rate constant

Abstract

A monoclonal antibody (MAb), ECL2B-2, was obtained by immunizing a peptide possessing a part of a sequence of a chemokine receptor, CCR-5, which is present as a membrane protein on the macrophage surface, and which plays an important role in human immunodeficiency virus (HIV) infection. From the DNA and the deduced amino acid sequences of the light and heavy chains of ECL2B-2 MAb, molecular modeling was conducted to calculate the steric conformation of the antibody. Modeling suggested that the structure of ECL2B-2 could possess one or two catalytic triad(s), composed of Asp(1), Ser(27a) (or Ser(27e)), and His(93) (or His(27d)), in the light chain of ECL2B-2. The three amino acid residues, Asp(1), Ser(27a), and His(93), are identical to those of catalytic antibody light chains such as VIPase and i41SL1-2. The light chain of ECL2B-2 MAb degraded the antigenic peptide CCR-5 within about 100 h. Surprisingly, the light chain had a very high catalytic reaction rate constant (k(cat)) of 2.23 min(-1), which is greater by factors of tens to hundreds than those of natural catalytic antibodies obtained previously. The heavy chain of ECL2B-2 MAb, which has no catalytic triad because of a lack of His residue, did not degrade the CCR-5 peptide.

Catalytic Features and Eradication Ability of Antibody Light-chain UA15-L against Helicobacter pylori

“…The degradation of TP41-1 peptide by UA15-L followed the Michaelis-Menten equation, and its kinetic parameters were obtained as k cat ϭ 0.24 min Ϫ1 and K m ϭ 6.2 ϫ 10 Ϫ5 M (see supplemental Appendix S1). These values were similar to those of other catalytic antibodies reported so far (3,10,14,16). The heavy chain by itself or the whole antibody (UA15 mAb) did not show any catalytic activity in this assay.…”

“…Prior to the cleavage test for UreB protein and the purified urease of H. pylori, a peptide, TPRGPDRPEGIEEEGGERDRD (TP41-1), which has mostly been used for monitoring the catalytic activity of the antibody and/or its subunits (3,10,(12)(13)(14), was completely digested by the catalytic reaction of UA15-L. By this reaction, the catalytic activity of UA15-L was held constant, showing no induction time (3,(12)(13)(14)(15). In the cleavage assay of UreB and the urease, the UA15-L mentioned above was used.…”

Losac, the First Hemolin that Exhibits Procogulant Activity through Selective Factor X Proteolytic Activation

“…The discovery of catalytic antibodies, also known as abzymes, with several previously unexpected functions constitutes an example of such convergence (53)(54)(55)(56)(57)(58)(59)(60). Focusing on the findings reported here, special attention should be given to proteolytic antibodies.…”

Theory of proteolytic antibody occurrence

“…Two groups have published in this area, our own [19] and that of Uda and coworkers [20,21]. Immunization with the neuropeptide VIP yielded an IgG with K m in the very low nanomolar range and unconventional kinetics indicating suppression of VIP hydrolysis at elevated IgG concentrations.…”

“…• screening for the catalytic activity of spontaneously produced Abs in healthy organisms and individuals with immunological diseases [13][14][15][16][17][18]; • routine immunizations with ordinary antigens [19][20][21];…”