Functional significance of isoenzymes in thermal acclimatization. Acetylcholinesterase from trout brain.
1. The effects of acclimatization temperature on the catalytic properties of acetylcholinesterase from rainbow-trout brain were examined. 2. Trout brain acetylcholinesterase occurs in two distinct forms. A single ;warm' variant of the enzyme is present after acclimatization to 17 degrees C; a single ;cold' variant appears after acclimatization to 2 degrees C. Both forms are present in fish after acclimatization to an intermediate temperature. 3. The K(m) values of the enzyme variants for acetylcholine are temperature-dependent, the lowest values coinciding with the acclimatization temperature at which each enzyme was induced. 4. It is concluded that the K(m)-temperature relationship is adaptive, and that the critical process during thermal acclimatization, in cases where enzymes show sharp changes in K(m) with temperature, is the synthesis of a new enzyme variant that is better suited for catalysis and control of catalysis under the conditions of the acclimatized state.
D000110:Acetylcholinesterase / Q000032:analysis*; D000222:Adaptation, Physiological; D000818:Animals; D001921:Brain / Q000201:enzymology*; D004589:Electrophoresis, Disc; D007527:Isoenzymes; D007700:Kinetics; D012487:Salmonidae / Q000378:metabolism*; D013696:Temperature
D007527:Isoenzymes; D000110:Acetylcholinesterase