Table 3

The β-P of ATP is transferred to the glucan

SubstratePhosphate donor
[γ-33P]ATP [β-33P]ATP (+ [γ-33P]ATP)
− R1, cpm+ R1, cpm− R1, cpm+ R1, cpm
Amylopectin4349311,512
Elongated glycogen604216110,423
Glycogen + G1P + Pho5923345110,749
  • Buffer C was used supplemented with either 2 mg of potato amylopectin, 1.4 mg of postelongated glycogen (see Materials and Methods), or 0.5 mg of glycogen, G1P, and phosphorylase (coelongation assay) and 0.5 mM ATP. Either 1.1 μCi [γ-33P]ATP or 1.1 μCi of a preparation in which [γ-33P]ATP had been partly converted to [β-33P]ATP (see Materials and Methods) were added. Reactions were started by addition of R1 (2.6 μg each) and terminated after 15 h. The radioactivity incorporated into the glucan was counted.