DNA-hydrolyzing activity of sIgA-abzymes of human milk is differentially inhibited by nucleoside triphosphates

Abstract

It is known that human milk contains secretory immunoglobulines A (sIgA-abzymes) possessing affinity to mammalian DNA and capacity to cleave plasmid DNA. Regulation of DNA-hydrolyzing activity of those sIgA-abzymes is poorly studied. Here we investigate the effect of nucleoside triphosphates towards the DNase activity of sIgA-abzymes which were purified from human milk by a sequential chromatography on protein A-agarose, DEAE-Fractogel, and DNA-cellulose. By using DNA-hydrolysing assay, we revealed that 1 mM ATP and 1 mM dATP markedly reduced the cleavage of linear form of plasmid DNA by sIgA-abzymes, while the effect of GTP, CTP, TTP and dGTP was much weaker. dCTP and dTTP did not influence DNase activity of the sIgA-abzymes. Possible mechanisms of nucleotide-mediated inhibition of the DNase activity of sIgA-abzymes are discussed.