Jake Sieger Biochem Final Study Guide Gluconeogenesis Be able to draw the substrates and products name the enzymes and know the general features for the enzymes of gluconeogenesis Pyruvate concerted to PEP o Endergonic reaction and is coupled with the hydrolysis of both ATP and GTP o 1 Pyruvate carboxylase converts Pyruvate to Oxaloacetate Biotin prosthetic group as a cofactor Lys residue Carboxyl group transfer Synthesized by intestinal bacteria deficiency is rare but can occur by ingestion of avidin Biotin avidin strongest non covalent interaction in nature Carboxylation involves bicarbonate Enzyme is mitochondrial in eukaryotes Product is an intermediate in Krebs cycle Enzyme is allosterically activated by acetyl CoA Activation by the product of opposing pathway o 2 Phosphoenolpyruvate carboxykinase converts Oxaloacetate to phosphoenolpyruvate No allosteric regulation Enzyme is regulated at level of transcription synthesis degradation Glucagon cAMP PKA increase PEPCK Insulin the reverse Next Six reactions o Reverse of glycolysis o 3 enolase converts Phosphoenolpyruvate to 2 phosphoglycerate o 4 phophglycerate mutase converts 2 phosphoglycerate to 3 o 5 phosphoglycerate kinase converts 3 phosphoglycerate to 1 3 phosphoglycerate bisphosphoglycerate o 6 GAP dehydrogenase converts 1 3 bisphosphoglycerate to Glyceraldehyde 3 phosphate and Dihydroxyacetone phosphate o 7 Triose phosphate isomerase converts GAP to DHAP o 8 Aldolase converts DHAP to Fructose 1 6 bisphosphate Last two steps of gluconeogenesis o 9 Fructose 1 6 bisphosphatase converts fructose 1 6 bisphosphate to fructose 6 phosphate Bisphosphate Negative allosteric regulation by AMP and Fructose 2 6 Reciprocal to regulation of PFK 1 except phosphoenolpyruvate o 10 Glucose 6 phosphatase converts fructose 6 phosphate to Glucose Restricted to liver kidney small intestine Used to release glucose for other tissues Not present in muscle Enzyme localized at luminal side of ER membrane Understand the reciprocal regulation of gluconeogenesis relative to glycolysis including the allosteric control of F2 6 bisphosphatase the allosteric activation of pyruvate carboxylase by Ac CoA and the hormonal gene induction of PEPCK Gluconeogenesis vs Glycolysis o 3 irreversible steps of Glycolysis are replaced with 4 irreversible steps of Gluconeogenesis Pyruvate kinase replaced with pyruvate carboxylase and phophoenolpyruvate carboxykinase Phosphofructokinase replaced with Fructose 1 6 bisphosphatase Hexokinase replaced with Glucose 6 phosphatase Regulation of Metabolic Pathways o Product inhibition Product in a pathway inhibits an enzyme allosterically earlier in the pathway to prevent product accumulation No need to invest energy to create additional product if its already there o Feed Forward Activation An early product in the pathway after committed step activates an enzyme allosterically later in the pathway to increase final product formation If there is accumulation of intermediate product there needs to be activation to increase the rate of overall pathway o Pyruvate kinase Inhibited by ATP and phosphorylation catalyzed by PKA Activated by Fructose 1 6 bisphosphate o Pyruvate decarboxylase Activated by acetyl CoA o PFK 1 Inhibited by citrate and ATP Activated by AMP and Fructose 2 6 bisphosphate o Fructose 1 6 bisphosphatase Inhibited by ATP and Fructose 2 6 bisphosphate Fructose 2 6 bisphosphate o Bifunctional regulatory enzyme of PFK2 FBP2 o Abundance of Glucose 6 phosphate leads to high levels of Frutose 2 6 bisphosphate which activates PFK 1 and inhibits FBPase 1 o Fructose 2 6 bisphosphate is produce from Fructose 6 phosphate by PKF2 o Fructose 2 6 bisphosphate is broken down to Fructose 6 phosphate by FBPase 2 o In liver PFK 2 is activated under abundance of glucose FBPase 2 is activated under scarce amounts of glucose Be able to list non carbohydrate precursors of gluconeogenesis discussed in class pyruvate lactate alanine glycerol glutamate aspartate Pyruvate oxaloacetate Lactate pyruvate oxaloacetate Alanine pyruvate oxaloacetate Glycerol dihydroxyacetone phosphate All other amino acids except Leucine and Lysine oxaloacetate Be able to name the eukaryotic locations of the two reaction steps in glycolysis and gluconeogenesis that do not occur in the cytosol ie the glucose 6 phosphatase reaction that occurs in the ER and the pyruvate carboxylase reaction that occurs primarily in the mitochondrial matrix 10 Glucose 6 phosphatase converts fructose 6 phosphate to Glucose Restricted to liver kidney small intestine Used to release glucose for other tissues Not present in muscle Enzyme localized at luminal side of ER membrane Pyruvate carboxylase converts Pyruvate to Oxaloacetate Biotin prosthetic group as a cofactor Lys residue Carboxyl group transfer Synthesized by intestinal bacteria deficiency is rare but can occur by ingestion of avidin Biotin avidin strongest non covalent interaction in nature Carboxylation involves bicarbonate Enzyme is mitochondrial in eukaryotes Product is an intermediate in Krebs cycle Enzyme is allosterically activated by acetyl CoA Activation by the product of opposing pathway Be able to list or trace the points of production in gluconeogenesis and the amount of ATP NADH required to run it relative to glycolysis Above Cori Cycle Understand the role of the Cori cycle and or the glucose alanine cycle in supplying gluconeogenic precursors o Couples fast glucose consumption in muscle and RBC and glucose regeneration in liver o NAD for glycolysis Alanine Cycle o Couples glucose consumption in muscle and glucose regeneration in o Transports NH3 to liver for utilization energy consuming o Doesn t effect NADH level NADH can be used to aerobic generation of liver ATP o Transamination reaction Pyruvate converted to alanine via alanine aminotransferase and glutamate a ketoglutarate Glycogen metabolism Know the reactions substrates and products of glycogen formation glucose P activation glycogen priming by glycogenin elongation by glycogen synthase branching by branching enzyme Glycogenesis o Production of glycogen from glucose o Glycogen energy storage in animals and fungi branched polysaccharide o Mitochondria Produced and stores in liver and muscle Krebs cycle Respiratory chain Chemi osmotic ATP production Fatty Acid breakdown o Cytoplasm Glycolysis Most of gluconeogenesis Glycogenesis Glycogenolysis Fatty acid synthesis o Phosphoglucomutase converts Glucose 6 phosphate to Glucose 1 phosphate Traps glucose in