Metabolism of Brached Chain Amino Acid (Valine, Isoleucine, Leucine)
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Branched chain amino acids include leucine, isoleucine, and valine. They are broken down by the branched chain alpha-ketoacid dehydrogenase complex in mitochondria. A defect in this enzyme can cause branched chain ketoaciduria, where patients accumulate branched chain amino acids and their keto acids in their urine, which smells like maple syrup or burnt sugar. This rare genetic disorder impairs other amino acid transport and protein synthesis, and can lead to seizures, vomiting, ketoacidosis, coma, and death if not treated with a low-branched chain amino acid diet and thiamine supplementation.
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Metabolism of Brached Chain Amino Acid (Valine, Isoleucine, Leucine)
- 2. Branched Chain Amino Acids
- 6. Based on the products obtained from the carbon skeleton, the branched chain amino acids are either…
- 7. Valine α-ketoisovalerate Isoleucine Leucine α-keto-β- methylvalerate α-ketoisocaproate Isobutyryl CoA 2-methylbutyryl CoA Isovaleryl CoA Methylacrylyl-CoA Triglyl CoA β-methylcrotonyl CoA HMG CoA Acetoacetate Propionyl CoA Acetyl CoA T r a n s a m i n a t i o n T r a n s a m i n a t i o n Methylmalonyl CoA α - K e t o a c i d D e h y d r o g e n a s e Biotin Propionyl CoA Methylmalonyl CoA Glucose Fat CO2 CO2 CO2 CO2 Glucose CO2 Biotin
- 8. Branched chain α-ketoacid Dehydrogenase Complex Mitochondrial enzyme Multi-enzyme complex Decarboxylase Transacylase Dihydrolipoyl dehydrogenase. Co-Enzymes - NAD Co-A Lipoic acid FAD TPP.
- 9. β-methylcrotonyl CoA HMG CoA Acetoacetate Acetyl CoA
- 10. Triglyl CoA Methylacetoacetyl CoA Propionyl CoA Acetyl CoA Lyase
- 11. Methylacrylyl CoA Propionyl CoA Succinyl CoA Methylmalonyl CoA Glucose
- 13. The urine of the affected individuals smells like maple syrup or burnt sugar Other name: Branched chain Keto aciduria Genetic: An autosomal recessive disorder. Incidence : fewer than 1 in 1,00,000 individuals. Enzyme defect: Branched chain α-ketoacid dehydrogenase, The net outcome: blockade in the conversion of α- keto acids to the respective acyl CoA thioesters. Leads to: Accumulation and excretion of branched amino acids and their keto acids.
- 14. Accumulation of BCAAs causes an impairment in transport & function of other amino acids. Protein biosynthesis is reduced. BCAAs competitively inhibit glutamate dehydrogenase.
- 15. Clinical Features – Severe M.R, Convulsions, Vomiting, Acidosis (ketoacidosis), Coma and Death.
- 16. Diagnosis- An early diagnosis by Enzyme Analysis. Plasma & Urine - ↑ Leu , Ile , Val and their α-ketoacids . Smell of Urine – Burnt Sugar Chromatography of Urine. Rothera’s Test - + ve. Rx – Diet low in BCA. High in Thiamine.