Enzyme activity in cryobiological systems: III. Low-temperature properties of honeybee glyceraldehydephosphate dehydrogenase

Abstract

Certain properties of honeybee and rabbit muscle GPDHs have been examined in vitro. While incubation of rabbit muscle GPDH at 0 °C in the presence of 4 m m ATP results in its dissociation, the enzyme from honeybees retains its native tetrameric structure. Furthermore all adenine nucleotides tested caused some inactivation of rabbit muscle GPDH but had either only a slight effect or none at all on the honeybee enzyme. However, both enzymes are competitively inhibited by ATP, ADP, and AMP and 3′,5′-AMP. In the absence of ammonium sulfate and ATP, honeybee GPDH was partially inactivated at 0 °C while the rabbit muscle enzyme was not affected. Inactivation of honeybee GPDH could be presented by low concentrations of ammonium sulfate. The honeybee enzyme retains essentially full activity over the pH range 6.5–8.0 when incubated with 10 m m ATP at 0 °C, while the rabbit muscle enzyme has been shown to be completely inactivated over this pH range in the presence of 2 m m ATP at 0 °C. On the basis of studies with adenine nucleotides it is concluded that insect GPDHs probably have evolved a capability for catalytic function at low temperature while retaining the ability to have this function controlled by these compounds.