Question

List major cofactors of metabolic enzymes discussed in this course, point out their precursors, describe their roles in metabolic reactions, and provide one reaction for each cofactor participates as an example of a general pattern. It does not have to be all the metabolic pathways listed but please be at least 3 or 4. The metabolic pathways are

1). Krebs cycle

02). Oxidative phosphorylation

03). Glycolysis and lactate formation

04). Glycogen synthesis & breakdown

05). Gluconeogenesis

06). Beta oxidation of fatty acids

07). Pentose phosphate pathway

08). Biosynthesis of fatty acids & phospholipids

09). Biosynthesis of cholesterol & cholesterol dynamics

10). Biosynthesis of amino acids & one carbon units

11). Biosynthesis of nitrogenous molecules

12). Disposal of nitrogenous molecules & urea cycle

Answer 1

NOTE: Reactions are depicted as

substrate ENZYME (cofactor is implied) product

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Krebs cycle

Cofactor: Coenzyme A (CoA)

Precursor: Vitamin B5

Example reaction: -ketoglutarate -ketoglutarate DEHYDROGENASE Succinyl-CoA

Role: acts as a carrier for the acyl group

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Cofactor: NADP

Precursor: Vitamin B3

Example reaction: Isocitrate ISOCITRATE DEHYDROGENASE -Ketoglutarate

Role: accepts electrons

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Cofactor: FAD

Precursor: Vitamin B2

Example reaction: Succinate SUCCINATE DEHYDROGENASE Fumarate

Role: accepts electrons

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Beta oxidation of fatty acids

Cofactor: FAD

Precursors: Vitamin B2

Example reaction: Palmitoyl-CoA ACYL-CoA DEHYDROGENASE trans-2-Enoil-CoA

Role: accepts electrons

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Cofactor: NAD

Precursor: Vitamin B3

Example reaction: L--hydroxy-Acil-CoA -hydroxy-Acil-CoA DEHYDROGENASE -cetoacil-CoA

Role: accepts electrons

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Cofactor: Coenzyme A (CoA)

Precursor: Vitamin B5

Example reaction: -cetoacil-CoA ACYL-CoA ACETYLTRANSFERASE Myristoyl-CoA

Role: acts as a carrier for the acyl group

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Glycolysis and lactate formation

Cofactor: Mg2+

Example reaction: Glucose HEXOKINASE Glucose-6-phosphate

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Cofactor: Thiamin piro-phosphate (TPP).

Precursor: Vitamin B1 (Thiamin)

Example reaction: PyruvatePYRUVATE DECARBOXYLASE Acetaldehyde

Role: important for the break of adjacent bonds to a carbonyl group

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Cofactor: NAD

Precursor: Vitamin B3

Example reaction: Glyceraldehyde-3-phosphateGLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE 1,3-bisphosphoglycerate

Role: accepts electrons

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