Phosphorylases

Phosphorylase inhibitors act on glycogen and thymidine phosphorylases, which cleave bonds by phosphorolysis. Glycogen phosphorylase releases glucose 1-phosphate from glycogen and controls the rate of glycogen breakdown in liver and muscle. CP-91149, reported in 1998, inhibits human liver glycogen phosphorylase and lowered blood glucose in diabetic mice. Ingliforib, BAY R3401 and GPi688 are further glycogen phosphorylase inhibitors for studies of hepatic glucose output. Thymidine phosphorylase converts thymidine to thymine and was identified in 1992 as the angiogenic platelet-derived endothelial cell growth factor. Tipiracil hydrochloride inhibits this enzyme, whereas doxifluridine is a fluoropyrimidine prodrug that thymidine phosphorylase activates.