Background:Recently, amylolytic activity was detected in IgMs isolated from the sera of the patients with multiple sclerosis.Material/Methods: All purified samples of IgM were electrophoretically homogenous and did not contain any co-purified α-amylase and α-glucosidase activities, in accordance with a set of criteria developed for abzymes. The amylolytic activity of abzymes was studied in the hydrolysis of p-nitrophenyl α-D-maltooligosaccharides with different degrees of polymerization from 1 to 8 by TLC and reverse-phase HPLC techniques.Results: All IgM samples isolated from 54 patients with clinically definite multiple sclerosis demonstrated hydrolytic activity towards the above artificial substrates. The Michaelis constant values (Km) in the hydrolysis of p-nitrophenyl α-D-maltoheptaoside were in the range of 10 p-nitrophenyl or p-nitrophenyl α-D-glucosides, thus indicating the presence of an α-D-glucosidase activity. For a number of the investigated samples, specific amylolytic activity increased depending on the length of substrates (from p-nitrophenyl maltopentaoside to p-nitrophenyl maltohexaoside); for other IgMs, the opposite dependence was observed. All IgMs studied did not exhibit any other glycoside hydrolase activities toward p-nitrophenyl glycoside substrates.Conclusions: Abzyme fractions from different donors demonstrated catalytic heterogeneity in Michaelis-Menten parameters and different modes of action in the hydrolysis of p-nitrophenyl maltooligosaccharides. Enzymatic properties of the IgMs tested varied from human a-amylases. All investigated abzyme samples did not show transglycosylating ability.

Keywords: Nitrobenzenes - chemistry, Adult, Amylases - metabolism, Antibodies, Catalytic - blood, Chromatography, High Pressure Liquid, Female, Humans, Immunoglobulin M - metabolism, Male, Middle Aged, Multiple Sclerosis - enzymology, Nitrobenzenes - chemistry, Oligosaccharides - chemistry