In maple syrup urine disease, the amino acids excreted in the urine are –
MAPLE SYRUP URINE DISEASE
- In this disorder, the branched-chain keto acids derived from isoleucine, leucine, and valine appear in the urine, giving it a maple syrup-like odor.
- This condition results from a deficiency in the branched-chain -keto acid dehydrogenase.
- It is a mitochondrial, enzyme complex consisting of a-ketoacid decarboxylase, dihydrolipoyl dehydrogenase, and Transacylase
- The early steps in the metabolism of these three amino acids are similar. One of the steps – decarboxylation is accomplished by a complex enzyme system i.e. branched-chain alpha-keto acid dehydrogenase using thiamine pyrophosphate (vitamin B1) as a coenzyme.
- The elevated keto acids cause severe brain damage, with death in the first year of life.
- The disease is characterized by feeding problems, vomiting, dehydration, severe metabolic acidosis, and a characteristic maple syrup odor to the urine. If untreated, the disease leads to mental retardation, physical disabilities, and even death.
- Treatment. A few cases respond to megadoses of thiamine (vitamin B1). Otherwise, synthetic diets low in branched-chain amino acids are given.