TYROSINE PROTEIN-KINASE IN BOAR SPERMATOZOA - IDENTIFICATION AND PARTIAL CHARACTERIZATION

A protein-tyrosine kinase has been isolated from a detergent-soluble extract of boar spermatozoa, using poly(Glu, Tyr)4:1 as a substrate. The purification procedure involves sequential 'column chromatographies on phosphocellulose, polyamino acid affinity and Sephadex G-100 molecular sieving, and results in more than a 1200-fold enrichment. Analysis of the most purified preparation by sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a major Coomassie blue-stained band of molecular mass 42 kDa. The Tyr-protein kinase does not seem to be autophosphorylable. The K(m) value for poly(Glu, Tyr)4:1 is relatively low, 2.3-mu-M, and the tyrosine-polymer phosphorylating activity is apparently inhibited by tyrphostin. The characteristics shown by this new tyrosine kinase - the first to be described in mature male germ cells - support the hypothesis that it belongs to the group of non-receptor-associated tyrosine kinases.