Fig. 7. cAMP-dependent protein kinase (PKA) activity in cell-free extracts of tentacles. Tentacles were collected, pooled and homogenized by mortar and pestle under liquid nitrogen followed by sonication for 2–4s in 1ml of ice-cold extraction buffer, pH6.8. The homogenate was then centrifuged at 20000g for 20min at 4°C. The supernatant was immediately used as the source of enzyme activity. PKA activity was assayed with 35µmoll-1 kemptide in the presence and absence of 0.1mmoll-1 exogenous cAMP using undiluted (filled columns) and 1:1 diluted (open columns) supernatants. The protein content of undiluted supernatants was 176µgml-1. Data are expressed as pmoles of phosphate transferred per minute. Values are means ± S.E.M. (N=2 experiments; n=4 samples).
