Influence of nucleic acids and polysaccarides on phosphotransferase activity of secretory immunoglobulin a from human milk

摘要

Influence of nucleic acids (DNA, t-RNA), synthetic oligonucleotides and polysaccarides (lipopolysaccarides Escherichia coli, heparine) on protein kinase and lipid kinase activity of human sIgA was studied. SIgA were isolated from human milk by chromatiography on ProteinA-Sepharose and DEAE-column(sIgAl), by affinity chromatography of sIgAl on DNA-cellulose (sIgA2) and by gel-filtration of sIgAl in buffer containing 5% of dioxane (sIgA3). Two ~(32)P-labelled products with high and low electrophoretic mobility in polyacrylamide gel with SDS were discovered after incubation of sIgA1 and sIgA2 with [#gamma#-~32P] ATP. The product with low elctrophoretic mobility degraded in 10% of trichloroacetic acid with formation of radioactive background in lanes of polyacrylamide gel. ~32P-labelled phospholipids were discovered among phosphorylation products. DNA (immobilised and in solution) increases lipid kinase activity of sIgA samples. In this case degradation of secretory component and sIgA H-chains was observed. Lipid kinase activity was precipitated in presence of heparin (1 mg/ml) and was isolated from sIgA by gel-filtration in buffer with 5% of dioxane. In so doing formation of ~32P-labelled products was taken place in presence of both [#gamma#-~32P] ATP and [~32P] orthophosphoric acid. Influence of synthetic deoxy-and ribooligonucleotides on casein kinase activity of sIgA3 was studied. It was observed that deoxyribooligonucleotides in micromolar concentrations increase casein phosphorylation in presence of sIgA and [#gamma#- ~32P]ATP. We suppose that catalytically-active sIgA possess affinity to DNA (antiDNA-sIgA) and can be present in human milk as a part of lipoprotein complexes.