Effects of seasonal change and prolonged anoxia on metabolic enzymes of Littorina littorea

The effects of seasonal change (July versus November) and prolonged anoxia (N-2 atmosphere at 5 or 10 degreesC for 6 days) exposure in vivo on the act ivities of 18 enzymes, as well as the kinetic properties of phosphofructoki nase (PFK) and pyruvate kinase (PK), were investigated in foot muscle and d igestive gland of the marine periwinkle Littorina littorea L. Seasonal diff erences in enzyme maximal activities were tissue-specific, with generally i ncreased activities during the summer and changes in a greater number of en zymes in digestive gland than in foot muscle. Seasonal differences in the k inetic properties of PFK and PK were observed in both tissues. PK from dige stive gland of winter animals showed a much higher S-0.5 for phosphoenolpyr uvate and stronger changes in enzyme kinetic properties in response to anox ia than did the enzyme in summer animals; this may suggest the presence of seasonal isozymes. The effects of anoxia were tissue- and season-specific. Anoxia exposure during the winter induced a greater number of changes in en zyme maximal activities in foot muscle than in digestive gland. Anoxia-indu ced changes in the kinetic properties of both PFK and PK were also seen in both organs. For PK, these changes were consistent with less active enzyme forms in the anoxic state. Hence, both seasonal and environmental (anoxia) factors influence enzyme maximal activities and kinetic properties in L. li ttorea.