The characterization of a UDP-N-acetylglucosamine: Gal beta 1-4Glc(NAc) beta 1-3 N-acetylglucosaminyltransferase in fluids from rat rete testis

Using Gal beta 1-4GlcNAc or Gal beta 1-4Glc as substrates, the UDP-N-acetylglucosamine: Gal beta 1-4Glc(NAc)beta 1-3-N-acetylglucosaminyltransferase (GlcNAcTase) activity of rat rete testicular fluid was investigated with respect to the effects of pH and of divalent metal ions, apparent K-m value, acceptor specificity and identity of products. The enzyme, whose activity was dependent absolutely on the presence of Mn2+, had an optimum pH of 7.5. It was completely inhibited by EDTA, Zn2+ and gossypol, and partially by Co2+ and Ca2+. Triton X-100 (1%) had not effect. When several oligosaccharides were tested as accepters, the highest affinity was found with Gal beta 1-3[Gal beta 1-4GlcNAc beta 1-6]Gal beta 1-4Glc. With Gal beta 1-4Glc as acceptor, the product was identified from its H-1-NMR spectrum as GlcNAc beta 1-3Gal beta 1-4Glc (lacto-N-triose II) by reference to the spectrum of authentic lacto-N-triose II. Both testicular and epididymal fluids showed GlcNAcTase activity. In epididymis the specific activity increased gradually from the proximal caput to the proximal cauda.