HUMAN BREAST-MILK IMMUNOGLOBULINS-G HYDROLYZE NUCLEOTIDES

Catalytically active antibodies, abzymes, appear in the blood of mamma ls immunized with the analogs of transition state or in the case of au toimmune diseases. Until recently, it was not shown whether abzymes ex ist in the blood of apparently healthy subjects. We have discovered th at secretory IgA (sIgA) from the milk of healthy mothers catalyze phos phorylation of a variety of proteins and that IgG can hydrolyze DNA an d RNA. In this study for the first time it is shown that IgG from huma n milk (and their Fab-fragments) also catalyze hydrolysis of nucleosid e mono-, di-, and triphosphates. The data meet certain stringent crite ria, unambiguously indicating that the observed catalytic activity is associated with IgG rather than contaminating enzymes. Although the nu cleotide-binding site of IgG is located in the light antibody chain, L -chains per se cannot hydrolyze NTP unlike the DNA-hydrolyzing abzymes . Kinetic and thermodynamic parameters that characterize the interacti on of NTP and dNTP with IgG-abzymes were analyzed. Possible reasons fo r appearance of polyclonal abzymes with different catalytic activities in the milk of healthy mothers are considered.