15. (12 pts) Indicate which cofactors are necessary for each metabolic reaction
ID: 269691 • Letter: 1
Question
15. (12 pts) Indicate which cofactors are necessary for each metabolic reaction below. If more than one co-factor is necessary, please indicate all of them. Not all co-factors shown below may be used Reduction: (ex. conversion of pyruvate to lactate -lactate dehydrogenease) Decarboxylation (ex. conversion of pyruvate into acetyl-CoA pyruvate dehydrogenase) Phosphorylation (ex. conversion of succinyl-CoA into succinate succinyl-CoA synthase) Carboxylation (ex. conversion of pyruvate into oxaloacetate - pyruvate carboxylase) Oxidation (ex. conversion of malate to oxaloacetate malate dehydrogenase) Phosphorylation (ex. conversion of glucose to glucose-6-P - hexokinase) Cofactors TPP Biotin Pyridoxal phosphate (PLP) ATP ADP FAD+ FADH2 NAD+ NADH Lipoic Acid Coenzyme A NADP+ NADPHExplanation / Answer
Reduction: Conversion of pyruvate to lactate is done using lactate dehydrogenase enzyme which needs NADH as cofactor. It also converts NADH to NAD+ which is used for glycolysis and energy production in cells.
Decarboxylation: Conversion of pyruvate to Acetyl-CoA is done through pyruvate dehydrogenase enzyme. It is a complex enzyme consisting of three different enzymes (E1, E2, E3) whose functions are different along with need for different cofactors. E1 is pyruvate dehydrogenase or decarboxylase and the cofactor it needs is Thiamine pyrophosphate (TPP) with which it forms a covalent bond. E2 is Dihydrolipoyl transacetylase and it uses lipoamide and coenzyme A as cofactors. E3 is Dihydrolipoyl dehydrogenase and the cofactors it uses are Flavin adenine dinucleotide and Nicotinamide adenine dinucleotide+ (NAD+).
Phosphorylation: Conversion of Succinyl coA into succinate through enzyme succinyl-coA-synthetase and NDP (ADP or GDP) is used as a cofactor.
Carboxylation: Conversion of pyruvate to oxaloacetate through enzyme pyruvate carboxylase needs Biotin as prosthetic group and Acetyl CoA for the reaction.
Oxidation: Conversion of malate to oxaloacetate through malate dehydrogenase needs NAD+ as the cofactor.
Phosphorylation: Conversion of glucose to glucose-6-P through the enzyme hexokinase needs ATP for the reaction to continue.
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