Proteolysis activity of IgM antibodies from rheumatoid arthritis patients' sera: evidence of atypical catalytic site

Abstract

The IgM antibodies from rheumatoid arthritis (RA) patients' sera were screened for peptide hydrolyzing activity. Recovery of structurally intact IgM antibodies (Abs), in a single step, was achieved using a weak anion-exchange methacrylate monolith disk. The IgM Abs from patients' sera hydrolyzed the Pro-Phe-Arg-4-methyl-coumaryl-7-amide (PFR-MCA) substrate appreciably compared to the healthy donors. The apparent K m values of IgM Abs from patients' sera were between 0.4 and 0.7 mM. Furthermore, IgM Abs displayed 5 to 10-folds greater proteolysis activity than IgG Abs, recovered from the same pathological serum. The proteolysis activity, as a function, was found to be independent of IgM-RF titer value. Affinity labeling approach targeted at the catalytic site histidine was studied, using a specific irreversible inhibitor, N-a-tosyl-L-lysine chloromethyl ketone (TLCK). Despite modification of catalytic His, observation of serine protease like activity suggest presence of an atypical catalytic framework in a few pathological IgM Abs.

Purification and characterization of an extracellular uricase from a new isolate of Sphingobacterium thalpophilum (VITPCB5)

“…The high selectivity and extension to a wide variety of ligand chemistry with CIM media have gained attention in the area of bio separation [35]. There are already several reports on purification of macromolecules like DNA, RNA, viruses like particles, IgM, IgG and enzymes using CIM ion exchange systems [35][36][37][38][39][40]. In our study, we used a CIM-CM disk for the purification of uricase enzyme.…”

Constant Domain-regulated Antibody Catalysis

“…Polyclonal antibody studies indicated that the average catalytic activity of IgMs far exceeds that of IgGs (15,19,35). IgGs develop from IgMs by a switch of C-domain gene usage, usually accompanied by immunogen-driven adaptive accumulation of V-domain mutations.…”

“…The same conclusion may be reached from the substrate classes sensitive to catalytic antibodies that are produced constitutively with no requirement for exposure to an external immunogen. Very small peptide "microantigens"' are hydrolyzed by antibody V-domains without the involvement of traditional high affinity noncovalent binding interactions that are developed adaptively by immunogen-driven B cell clonal selection (14,15). The same hydrolytic reaction is catalyzed frequently by Bence Jones proteins, light chains produced by multiple myeloma patients (16,17).…”

Proteolytic activity of IgG-antibodies of mice, immunized by calf thymus histones

“…Встановлено, що 7 із 8 препаратів IgGантитіл сироватки крові хворих на ревматоїдний артрит Ревматоїдний артрит -це системне за-хворювання сполучної тканини з переваж-ним ураженням дрібних суглобів за типом ерозійнодеструктивного поліартриту неясної етіології зі складним автоімунним патогене-зом. Нещодавно в сироватці крові хворих на ревматоїдний артрит було виявлено IgG і IgM антитіла, здатні гідролізувати синтетичний пептид ProPheArg4метилкумаринімід [34]. При цьому пептидазна активність IgMантитіл була на порядок вищою, ніж активність IgG антитіл.…”

“…дані про те, що у сироватці крові людей із сеп-сисом міститься високий рівень протеолітично активних IgGантитіл, здатних гідролізувати, подібно до IgMантитіл сироватки крові хворих на ревматоїдний артрит [34], синтетичний пеп-тид ProPheArg4метилкумаринімід [35,36]. При цьому титр протабзимів і рівень їхньої каталітичної активності позитивно корелює зі…”