Changes in GDH activity in the chela muscle of Cancer pagurus during the annual cycle. Effect of the moult stage

Abstract

1. 1. Glutamate dehydrogenase (GDH) activity was measured in the chela muscle of wild Cancer pagurus throughout an annual cycle. The effect of the crab's size/weight and moult stage on GDH activity was also examined. 2. 2. GDH activity in the glutamate formation reaction (A1) was inversely correlated to the crab's size/weight and was influenced by the moult cycle, especially in early postmoult when a 3-fold activity increase was observed. Therefore, the two activity levels, 80 mIU/mg prot and 110 mIU observed in summer and autumn/winter, respectively, resulted mainly from these factors. No clear seasonal variations were noticed. 3. 3. GDH activity in the ammonia formation reaction (A2) was not related to the crab's size/weight and not significantly influenced by the moult cycle. A relatively constant activity level fluctuating around 30 m IU/mg prot was observed throughout the year. 4. 4. The mean value of the activity ratio (A1:A2) was around 2.7:1 throughout the year, but the ratio presented a high variability between individual crabs of the same batch and between monthly batches of crabs. Changes in A1:A2 ratio always resulted from changes in A1 activity. 5. 5. GDH activities were higher in the propodus than in the carpus-merus, especially the A1 activity. 6. 6. Although the activity of GDH in muscle was generally higher in the glutamate formation reaction, it is suggested that the primary role of GDH was devoted to the reverse reaction.