Fig. 8. Effects of substrate concentration on cAMP-dependent protein kinase (PKA) activity in cell-free extracts of tentacles. Tentacles were pooled and processed for the assay of PKA activity as in Fig.6. The supernatant extract was immediately mixed with different concentrations of kemptide in the reaction mixture in the presence () or absence () of 0.1mmoll^-1 cAMP. The protein content of supernatants was 140µgml^-1. Data are expressed as pmoles of phosphate transferred per minute. Each data point represents the mean ± S.E.M. (N=2 experiments; n=4 samples).