Porphobilinogen Deaminase: Physiology, Biochemistry, and Organic Mechanism

The video explores the intricate process of heme synthesis, focusing on the enzyme porphobilinogen deaminase. It explains the enzyme's mechanism, including the rare E1 mechanism, and the synthesis of hydroxymethyl bilane. The video also covers the subcellular compartments involved in heme synthesis and the energetic demands of the process. Additionally, it discusses the implications of enzyme deficiencies, particularly acute intermittent porphyria, and the accumulation of porphobilinogen in the cytosol.

What is the primary function of the enzyme porphobilinogen deaminase in heme synthesis?

• To deaminate porphobilinogen

• To cyclize the porphyrin ring

• To transport intermediates to the mitochondria

• To synthesize delta-aminolevulinic acid

How many molecules of delta-aminolevulinic acid are required to synthesize one porphobilinogen?

• One

• Two

• Four

• Eight

Which subcellular compartment is the initial site for heme synthesis?

• Cytosol

• Mitochondrial matrix

• Endoplasmic reticulum

• Golgi apparatus

What is the role of the dyrol coenzyme in the mechanism of porphobilinogen deaminase?

• It stabilizes the carbocation intermediate

• It acts as a substrate for the reaction

• It polymerizes pyrrole rings

• It is incorporated into the final product

What type of reaction mechanism is involved in the first step of porphobilinogen deaminase?

• Radical substitution

• Electrophilic addition

• Unimolecular elimination

• Bimolecular nucleophilic substitution

How many cycles of unimolecular elimination and condensation occur in the mechanism of porphobilinogen deaminase?

• Four

• Two

• Three

• Five

What is the final product of the porphobilinogen deaminase reaction?

• Uroporphyrinogen

• Delta-aminolevulinic acid

• Hydroxymethyl bilane

• Porphobilinogen

What is the condition called when there is a deficiency of porphobilinogen deaminase?

• Acute intermittent porphyria

• Chronic porphyria

• Porphyrin accumulation disorder

• Heme deficiency syndrome

What happens to porphobilinogen in the cytosol when there is a deficiency of porphobilinogen deaminase?

• It is converted to heme

• It accumulates and causes toxicity

• It is broken down into amino acids

• It is transported to the mitochondria

Which of the following is NOT a consequence of porphobilinogen deaminase deficiency?

• Acute intermittent porphyria

• Potential toxicity

• Increased heme production

• Accumulation of porphobilinogen