Fig. 2. Glucose (Glc) phosphorylation to glucose-6-phosphate (Glc-6-P) by mitochondrially bound hexokinase with exogenous ATP or with ATP generated by oxidative phosphorylation. The rate of Glc phosphorylation was determined at equivalent [ATP], either added exogenously in the absence of oxidative phosphorylation (triangles) or generated by oxidative phosphorylation (circles). From either source, the [ATP] was subsaturating, with the rate of Glc phosphorylation well below that seen when the ATP levels were acutely raised by addition of saturating levels of exogenous ATP (squares). Reprinted with permission from BeltrandelRio and Wilson (1991).