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PEROXISOMES

• Peroxisome: General
  • Single-membrane organelle
  • Present in nearly all eukaryotic cells
• Peroxisome functions
  • H₂O₂ metabolism
  • Ether-Phospholipid biosynthesis
  • Bile acid; Cholesterol; Plasmalogen synthesis
  • β-Oxidation: Fatty acids (Long & Very long chain)
  • Very-long chain Fatty acid-CoA
    • Types: C26:0 & C24:0
    • Enzymes in pathway
      • Straight-chain acyl-CoA oxidase
      • D-bifunctional protein
      • Thiolases: 3-Ketoacyl-CoA thiolase; Sterol carrier protein X
  • Branched chain Fatty acid-CoA
    • Types
      • Pristanoyl-CoA
      • Bile acid intermediates: THCA; Dihydroxycholestanoic acid (DHCA)
    • Enzymes in pathway
      • Branched-chain acyl-CoA oxidase
      • D-bifunctional protein
      • Thiolase: Sterol carrier protein X
  • Other: Amino acid & Purine metabolism
• Peroxisome contents: > 60 enzymes
• Peroxisome disorders: Classification & Disorders
  • Single enzyme: Affects single metabolic pathway
    • Hyperoxaluria type I
    • Refsum disease
      • Phytanoyl-CoA hydroxylase
      • PEX7
      • Peroxin-1
    • Adrenoleukodystrophy
      • X-linked (ALDP)
    • Rhizomelic chondrodysplasia punctata (RCDP) : DHAPAT
    • β-Oxidation disorders
      • α-Methylacyl-CoA racemase (AMACR) deficiency
        • Type II
        • Type III (dihydroxyacetone phosphate acyltransferase)
      • D-bifunctional protein (DBP)
      • Straight-chain acyl-CoA oxidase
  • Peroxisomal biosynthesis
    • General
      • Disorders affect all of the metabolic pathways of peroxisome
      • Disorders can result from mutations in any > 14 genes: PEX genes
      • Peroxins: Products of PEX genes
      • PEX gene function: Peroxisome biogenesis
    • Disorders
      • Neonatal adrenoleukodystrophy (NALD): PEX10
      • Zellweger syndrome: PEX10
      • Infantile Refsum disease (IRD)
      • Rhizomelic chondrodysplasia punctata (RCDP), Type I
      • Mulibray nanism
• Peroxisome: External link