D-Lactate formation, D-LDH activity and glycolytic potential ofHelix pomatia L.

Abstract

1. InHelix pomatia the affinity of LDH for pyruvate is strongly temperature-dependent, ranging at pH 6.0 from 0.058 mM at 10°C to 0.124 mM at 25°C, and at pH 7.0 from 0.072 to 0.189 mM. 2. The affinity of the enzyme for D-lactate is 30–60 times lower than for pyruvate (xxx xxx ofKm=3.5 mM at 20°C) and is not temperature-dependent. 3. All five isoenzymes of LDH can be detected electrophoretically in ammonium sulfate precipitates of homogenates of the snail foot. Isoenzyme 4 was always present, 3 and 5 occurred in one-half and two-thirds respectively of all specimens investigated, while 1 and 2 could be detected only in summer animals. 4. Total LDH activity in winter animals is twice as high as in summer animals. 5. In hibernating animals the steady state concentration of D-lactate in the foot is 1.35 mM. In the excised foot, at room temperature D-lactate is formed at an average rate of 0.17 μmoles·min−1·(g fresh weight)−1. 6. Anaerobic pyruvate flux in the excised foot is about 20 times higher than aerobic pyruvate flux as determined by measuring the oxygen consumption of the hibernating animal. Maximum LDH activity in vitro exceeds the activity measured in vivo by a factor of 100, whereas in vertebrate muscles the factor is close to 10.