Table 1

The phosphorylation of glucans catalyzed by R1 depends on ATP

SubstratesPhosphate incorporation, nmol G6P/μmol Glc
ATP, PEP9.31 (9.29, 9.32)
ATP, PPi8.60 (9.52, 7.67)
ATP8.55 (7.81, 9.28)
PEP, PPiND
PEPND
PPiND
UTPND
GTPND
NoneND
  • Activity of R1 was determined using the coelongation assay. R1 (7.2 μg each) was incubated for 14 h with 0.5 mg glycogen, 40 mM G1P, 0.6 units of phosphorylase, and different possible phosphate donors (5 mM ATP, PEP, UTP, and GTP; 2.5 mM PPi). Following precipitation and hydrolysis of the polyglucan, G6P and glucose (Glc) were determined enzymatically. Values are means of two independent experiments. Values in parentheses are the individual measurements for experiments 1 and 2 (each run in duplicate). In controls (lacking R1) no phosphate incorporation was observed (not shown). ND, not detectable.