Kinetic properties of phosphofructokinase and hesokinase the Antartic fish

Specimens of Trematomus bernacchii were caught by hooks near the Japanese Antarctic Station of Syowa during the month of January, 1992. The caught animals were taken to the Laboratory at the Icebreaker Shirase. Epaxial and cardiac muscles were dissected, washed thoroughly with chilled saline and used for the preparation of phosphofructokinase (PFK) and hexokinase (HK). Liver, encephalon, and whole blood were also obtained and used for the preparation of crude extracts and hemolysates. The following kinetic data were obtained for PFK: the apparent Km for F-6-P in the presence of 216MuM of ATP; the apparent Km for ATP in the presence 1mM of F-6-P. In both cases, the experiments were carried out at 20 degrees Celsius, pH 8.0. At this pH, the fish PFK did not display allosteric properties. The allosteric behavior of this preparation of PFK was assayed at pH 7.0. Levels of HK assayed in tissues crude extracts and red blood cells hemolysates gave the following results in specific activity (mU/mg protein): cardiac muscle, 62; encephalon, 18; liver, 2.7; RBC hemolysates, 0.0; epaxial muscle, 0.0. The ATP and glucose apparent Km were assayed for the cardiac muscle HK.