Category: biosynthesis
Hepatic (+ renal cortex) synthesis of glucose from non-carb precursors (lactate, glycerol, glucogenic amino acids). Reverses 7 of 10 glycolytic steps via the same enzymes; 4 irreversible glycolytic steps are bypassed by 4 unique gluconeogenic enzymes: pyruvate carboxylase (mitochondrial; pyruvate → OAA, biotin-dependent), PEPCK (cytosolic; OAA → PEP), fructose-1,6-bisphosphatase (RATE-LIMITING; opposes PFK-1), glucose-6-phosphatase (microsomal lumen; only expressed in liver/kidney/intestine — hence those are the only gluconeogenic tissues). Cortisol + glucagon upregulate; insulin downregulates; metformin's primary action is to suppress hepatic gluconeogenesis.