Table 3.

The β-P of ATP is transferred to the glucan

Substrate	Phosphate donor
	[γ-33P]ATP		[β-33P]ATP (+ [γ-33P]ATP)
	− R1, cpm	+ R1, cpm	− R1, cpm	+ R1, cpm
Amylopectin	43	49	31	1,512
Elongated glycogen	60	42	161	10,423
Glycogen + G1P + Pho	59	233	45	110,749

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.