Gluconeogenesis
Gluconeogenesis est iter metabolicum, quod glucosum diversis ex substratis non carbohydratis format. Est iter ubiquitosum, quod in plantis, fungis, bacteriis allisque microorganismis inveniri queat. In vertebratis gluneogenesis imprimis in hepate, minore in parte in corticis renum occurrit. Una cum itinere metabolico glycogenolysis, quae ieiunio ineunte gluconeogenesi citius rogatur, iter glucogenesis glycaemiam (i. e. magnitudinem glucosi in sanguine) augeri servat, ita hypoglycaemiam evitare. Plurimis animalibus gluconeogenesis observatur ieiunio, fame, diaeta minus carbohydrata, exercitatione intensa ineunte. Gubernatio itineris per factores et inhibitores et activatores, ut insulinum, glucagonum, cortisolum, et alias substantias fit, et aequilibrium inter se multitudinem formationis glucosi determinat. Insuper cerebrum valores glucosi sanguinei sensit, et per neurona parasympathica autonomica liberatio glucagoni stimulatur, ut ita formatio glucosi augeatur. Intineris substantia communis initium est pyruvatum. Gluconeogenesis, formatio glucosi ex pyruvato imprimis per gradus quinque describi potest: Formatio oxaloacetati ope enzymi pyruvati carboxylasis (PC) et cofactoris vitamini B7 (biotini). Nota ut cyclus acidi citrici substratum oxaloacetati requirit, et oxaloacetatum praecipue in cellulis muscularibus in iter hoc transformatur ("anaplerosis") Formatio phosphoenolopyruvati (PEP) Formatio 2-phosphoglycerati ope enzymi enolasis, et formatio 3-phosphoglycerati ope phosphoglycerati mutasis, deinde 1,3- bisphosphoglycerati ope phosphoglycerati kinasis, postea glyceraldehydi 3-phosphati ope glyceraldehydi 3-phosphati dehydrogenasis, denique fructosi-1,6 bisphosphati ope aldolasis A Gradus proximus velocitatem gluconeogensis terminat: dephosphorylatio ex fructoso-1,6 bisphosphato in fructosum-6 phosphatum ope enzymi fructosi-1,6 bisphosphatasis et cofactorum Mg2+ et Mn2+. Ex fructoso-6 phosphato oritur glucosum-6 phosphatum. Hydrolysis glucosi-6 phosphati in glucosum, ope enzymi glucosi-6 phosphatasis In diabete mellito resistentia contra insulinum occurrit ut restrictio glucogenesis commutata sit, ita hyperglycaemia apparere potest.