BCH 361 Lecture Notes - Lecture 4: Pyruvate Carboxylase, Phosphoenolpyruvate Carboxykinase, Acetyl-Coa
12 Jan 2017
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Gluconeogenesis: synthesis of glucose molecules from non-sugar precursor molecules (pyruvate, lactate, glycerol, aa). Goal of first 2 steps: bypass the last highly exergonic irreversible step 10 pf glycolysis (pep -> pyruvate). To bypass the very endergonic reverse step (pyruvate -> pep), we create a 2-step process in which pyruvate -> pep by using a favorable rxn pathway. Step 1a) carboxylation of pyruvate -> oxaloacetate by pyruvate carboxylase (mitochondrial matrix) Pyruvate is carboxylated at bottom of c3 to yield oxaloacetate via a pyruvate carboxylase which hydrolyses an atp. Couple this endergonic process w/ exergonic hydrolysis of atp. Pyruvate carboxylase consists of 4 identical subunits a) b) Biotin-binding domain contains biotin which binds the co2 and brings it to active site of pyruvate carboxylase. Atp-binding is used to make co2 more reactive because otherwise, requires input of e to attach to pyruvate. Carboxybiotin tends to decarboxylate and needs protection from h2o. Recall: in body fluids, don"t have co2 dissolved bc it"s non-polar.
