Topic 11: Coenzymes Decarboxylation

Which coenzyme is involved in the non-oxidative decarboxylation of α-keto carboxylates?

• Thiamin Pyrophosphate (TPP)

• Pyridoxal Phosphate

• Biotin

• Coenzyme A

What type of reaction is associated with Pyridoxal Phosphate?

• Methylation

• Phosphorylation

• Decarboxylation

• Hydroxylation

Which reaction is NOT associated with Thiamin Pyrophosphate (TPP)?

• Retro-aldol condensation

• Racemization

• Non-oxidative decarboxylation

• Oxidative decarboxylation

Which of the following is a reaction type associated with Thiamin Pyrophosphate (TPP)?

• Hydration

• Carboxylation

• Retro-aldol and aldol condensations

• Transamination

Which coenzyme is primarily involved in transamination reactions?

• Pyridoxal Phosphate

• Thiamin Pyrophosphate (TPP)

• Coenzyme A

• Biotin

What type of reaction is NOT typically associated with Pyridoxal Phosphate?

• Racemization

• Transamination

• Decarboxylation

• Carboxylation

Which of the following vitamins is a cofactor for the enzyme responsible for the carboxylation of pyruvate to form oxaloacetate?

• Pantothenic acid (B5)

• Niacin (B3)

• Thiamine (B1)

• Riboflavin (B2)

Answer explanation

Thiamine (B1) is a cofactor for the enzyme pyruvate dehydrogenase, which catalyzes the carboxylation of pyruvate to form acetyl-CoA.

Lipoic acid is a coenzyme for:

• pyruvate hydroxylase

• pyruvate carboxylase

• pyruvate dehydrogenase

• alpha-ketoglutarate dehydrogenase

• citrate lyase

Which of the following reactions involves the coenzyme Thiamin Pyrophosphate (TPP)?

• non-oxidative decarboxylation

  of α-keto carboxylates

• oxidative decarboxylation

• decarboxylation of amino acids

• retro aldol and aldol

  condensations

Draw the arrow-pushing mechanism for the transimination reaction between the amino acid and PP-Enzyme.