1. 1. Glycogen, caffeine and glucose dissociate phosphorylase a tetramer to dimers with half-maximum effect at 0.16%, 1.1 and 71 mM concentration, respectively, as monitored by crosslinking with dimethyl suberimidate at 18°C. 2. 2. The above ligands increase the rate of dephosphorylation and tryptic digestion of phosphorylase a at 18°C in the same way with half-maximum effect at 0.04%, 0.1 and 9 mM concentration, respectively. 3. 3. Caffeine and glucose acted synergistically in tetramer dissociation as well as in the enzymic modifications. 4. 4. The α-anomer of d-glucose was twice as effective as its mutarotational equilibrium solution.
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