EFFECTS OF ANOXIA AND QUIESCENCE ON PYRUVATE-KINASE FROM THE FOOT OF THE MANGROVE SNAIL LITTORINA-SCABRA-ANGULIFERA LAMARCK

Adult mangrove snails, Littorina scabra angulifera Lamarck, live above the high water mark whereas the juveniles are found intertidally. The adults have behaviors similar to those of terrestrial snails, particularly a quiescent phase in response to dry conditions. This study reports the changes observed in some kinetic parameters of pyruvate kinase during quiescence and exposure to anoxia. The apparent K(m(PEP)) of pyruvate kinase from the foot increased from 0.080 +/- 0.02 mmol.l-1 to 0.17 +/- 0.04 mmol.l-1 during 7 days of quiescence. There was no change in the activity of the enzyme in the tissue during the quiescent period. Exposure to anoxia for 12 h increased the apparent K(m(PEP)) from 0.080 +/- 0.02 mmol.l-1 to 1.2 +/- 0.4 mmol.l-1 while the activity decreased from 13.6 mumol.min-1.g wet wt.-1 to 4.7 mumol.min-1.g wet wt.-1. The changes induced by quiescence were readily reversed on forcible immersion for 1 h; those induced by anoxia were reversed when the animals were placed in air for 4 h. Alkaline phosphatase treatment could reverse the changes induced by anoxia, but had no effect on the enzyme from quiescent animals. This would suggest that anoxia induces a phosphorylation of the enzyme, but the mechanism underlying the changes during quiescence is different in some way.