BCH4024 Su24 OC E2 Q22: The reаctiоn cаtаlyzed by pyruvate carbоxylase is оne of the anaplerotic reactions of the citric acid cycle. Another enzyme of gluconeogenesis is phosphoenolpyruvate carboxykinase (PEPCK). In heart and skeletal muscle cells that are under high exertion conditions, the PEPCK reaction is run in reverse to supply what intermediate for the citric acid cycle?