Porphobilinogen Synthase: Physiology, Biochemistry, and Organic/Inorganic Mechanism

The video tutorial explores the synthesis of delta aminolevulinic acid in mitochondria and its transport to the cytosol for heme production. It highlights the role of porphobilinogen synthase in converting delta aminolevulinic acid to porphobilinogen, a precursor for heme and other molecules. The enzyme's inhibition by lead and its genetic deficiency, known as aminolevulinic acid dehydratase deficiency or DOS porphyria, are discussed. The video also delves into the enzyme's mechanism, focusing on the role of zinc and lysine residues in the active site.

What is the primary role of delta aminolevulinic acid in the cell?

• To synthesize proteins

• To produce heme

• To generate ATP

• To break down glucose

Which enzyme is responsible for converting delta aminolevulinic acid into porphobilinogen?

• Porphobilinogen synthase

• Cytochrome c oxidase

• Catalase

• Aminotransferase

What is a common inhibitor of porphobilinogen synthase?

• Calcium

• Lead

• Iron

• Magnesium

DOS porphyria is classified as which type of genetic disorder?

• Autosomal dominant

• X-linked recessive

• Mitochondrial

• Autosomal recessive

Which symptom is NOT typically associated with DOS porphyria?

• Skin sensitivity to sunlight

• Blistering and scarring

• Nausea and vomiting

• Increased appetite

What role does zinc play in the active site of porphobilinogen synthase?

• Acts as a reducing agent

• Chelates hydroxide

• Binds to oxygen

• Transfers electrons

What is the first step in the mechanism of porphobilinogen synthase?

• Release of water

• Cyclization of the substrate

• Deprotonation of lysine

• Formation of a Schiff base

What is formed when the lysine residue attacks the carbonyl group of delta aminolevulinic acid?

• A free radical

• A Schiff base

• A tetrahedral intermediate

• A cyclic compound

What is the final product of the porphobilinogen synthase mechanism?

• Vitamin B12

• Porphobilinogen

• Cytochrome c

• Heme

What happens to the lysine residues at the end of the porphobilinogen synthase mechanism?

• They are degraded

• They are phosphorylated

• They are regenerated

• They are oxidized