Pseudo-Zellweger syndrome: deficiencies in several peroxisomal oxidative activities
Insights
This study details a pseudo-Zellweger syndrome case with normal peroxisome numbers but deficient enzyme activity. The findings suggest a cofactor utilization defect rather than a peroxisome biogenesis issue.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Zellweger cerebrohepatorenal syndrome is a severe peroxisome biogenesis disorder.
- Peroxisomes are crucial for various metabolic processes, including fatty acid metabolism and bile acid synthesis.
Observation:
- An infant presented with symptoms mimicking Zellweger syndrome but with abundant peroxisomes in liver cells.
- Key peroxisomal enzymes like fatty acyl-CoA oxidase and D-amino acid oxidase showed significant reduction (80-85%).
- Deficiencies in bile acid and pipecolic acid oxidation were noted.
Findings:
- The case, termed "pseudo-Zellweger syndrome," exhibits multiple peroxisomal enzyme deficiencies, not a biogenesis defect.
- Specific enzymatic deficits impact fatty acid metabolism and bile acid oxidation.
- Accumulation of very long chain fatty acids was observed, alongside neuronal heterotopia, renal cysts, and adrenal atrophy.
Implications:
- This case highlights a distinct mechanism of peroxisomal dysfunction, separate from peroxisome biogenesis defects.
- The findings suggest a potential defect in flavin adenine dinucleotide (FAD) cofactor utilization.
- Understanding this specific enzymatic deficiency is crucial for diagnosing and potentially treating related metabolic disorders.
Abstract:
We describe an infant girl with a clinical, chemical, and pathologic syndrome remarkably similar to Zellweger cerebrohepatorenal syndrome but whose liver parenchymal cells contained abundant peroxisomes. Peroxisomal L-alpha hydroxy acid oxidase, catalase, and the plasmalogen synthesizing enzyme dihydroxy acetone phosphate-acyl transferase activities were normal; other peroxisomal enzymatic activities, including fatty acyl-CoA oxidase and D-amino acid oxidase, were reduced by 80% to 85%. Oxidation of bile acids and pipecolic acid was also deficient. Autopsy revealed the presence of neuronal heterotopia, renal cortical cysts, adrenal atrophy, and accumulation of very long chain fatty acids. The clinical and pathologic features of this case of "pseudo-Zellweger syndrome" reflect a deficiency in multiple peroxisomal activities rather than a defect in peroxisomal biogenesis. The deficient enzymatic activities require flavin adenine dinucleotide, and the underlying defect may be in the utilization of this cofactor.
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