Catalytic properties of IgMs with amylolytic activity isolated from patients with multiple sclerosis

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 alpha-amylase and alpha-glucosidase activities, in accordance with a set of criteria developed for abzymes. The amylolytic activity of abzymes was studied in the hydrolysis of p-nitropherryl alpha-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 (K-m) in the hydrolysis of p-nitropherryl alpha-D-maltoheptaoside were in the range of 10 mumole to 0.1 mM. A part of the IgMs exhibited the ability to liberate free p-nitrophenyl or p-nitrophertyl alpha-D-glucosides, thus indicating the presence of an a-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-nitrophertyl 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 alpha-nitrophenyl maltooligosaccharides. Enzymatic properties of the IgMs tested varied from human alpha-amylases. All investigated abzyme samples did not show transglycosylating ability.