Enzymic activity of the K5-type yeast killer toxin and its characterization

Izgu F., Altinbay D., Sertkaya A.

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY, cilt.69, sa.11, ss.2200-2206, 2005 (SCI İndekslerine Giren Dergi) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 69 Konu: 11
  • Basım Tarihi: 2005
  • Doi Numarası: 10.1271/bbb.69.2200
  • Sayfa Sayıları: ss.2200-2206


K5-type yeast killer toxin secreted by P. anomala NCYC 434 cells has a broad killing spectrum. Competitive inhibiton of killer activity showed that glucans, mainly the beta-1,3 glucan, represent the primary toxin binding site within the cell wall of sensitive cells. Its hydrolytic activity on laminarin in an exo-like fashion revealed that the toxin exerts its killing effect by exo-beta-1,3-glucanase activity. Its specific activity on laminarin was 120U/mg, and the Michaelis constants K-m, and V-max for laminarin hydrolysis were 0.25mg/ml and 370 mu mol/min/mg. The toxin exerted its cytocidal effect after 2 h contact with the target cells. Production of the toxin by the cells was induced only when they were grown in culture media rich in beta-glucan sources, and the addition of glucose increased the specific production rate. The enzymic activity of the toxin was fully inhibited by Hg+2, but increased with some other metal ions, most of all by Pb+2.