[Protein kinase activity of immunoglobulins in human blood plasma]

Protein kinase activity of the immunoglobulins (Ig) fractions from blood plasma of clinically healthy humans has been studied. IgA, IgG and IgM preparations have been obtained using column chromatography on sorbents with rabbit antibody to H-chains of human Ig. The level of 32P incorporation in casein in the presence of [gamma-32P]ATP was used to determine protein kinase activity of the Ig-fractions. The protein kinase activity of the preparation of IgA (but not IgG or IgM) was defined. The high-purified preparation of IgA for studing the protein kinase activity has been obtained. Three stages of purifications were used--the separation of plasma proteins by polyethylenglycol 6000, gel-filtration on the column with Toyopearl HW-60 Fine and affinity chromatography on the column containing rabbit antibody to H-chains of human IgA. It was revealed that the fraction of IgA possesses the casein phosphorylation activity. Heparin and trifluoperazine completely and partially inhibited protein kinase activity of IgA while spermidine did not render essential influence. On the basis of the obtained results the conclusion is made that the blood of clinical by healthy humans contains IgA possessing the protein kinase activity.