Maple Syrup Urine Disease (MSUD) is "an autosomal recessive metabolic disorder [caused by a deficiency in the branched-chain-alpha-keto acid dehydrogenase complex (BCKDC)." [1] This disease is named by the sweet smelling urine and/or earwax that is found in infants. If MSUD is not diagnosed during infancy, it may lead to severe brain damage and eventual death. It is approximately found in 1:180,000 infants. [2

Branched-Chain-Alpha-Keto-Acid Dehydrogenase Complex (BCKDC)Edit

This enzyme complex is a responsible for the catabolism of leucine, valine, and isoleucine. A mutation would cause a buildup of ketoacids in blood in urine, causing MSUD. BCKDC is found in the mitochondria and is part of the Kreb's cycle. It has 4 subunits: E1α, E1β, E2, and E3.  The E1α and E1β subunits are branched-chain alp
Beta polypeptide

Picture of the beta polypeptide.

ha-keto acid decarboxylase and their functions are to " catalyzes both the decarboxylation of the α-ketoacid and the subsequent reductive acylation of the lipoyl moiety." [3] The E1β subunit mutation is a cause of MSUD type 1B. The E2 subunit is a dihydrolipoamide branched chain transacylase which catalyzes the transger of the acyl group to coenzyme A. The E3 subunit is a " flavoprotein, and it re-oxidizes the reduced lipoyl sulfur residues of E2 using FAD."  This enzyme complex also requires 5 co-factors: thiamine pryophosphate, FAD, NAD+, Lipoate, and Coenzyme A.  

Associated SNPS with MSUDEdit

There are about 40 SNPs associated with the mutation of the E1β subunit. Scientists have done research on the Ashkenazi Jewish (AJ) popultion due to large number of families that are affected (10 of 34 families) [4]. Researchers state that this is due to the founder effect, which is a loss of genetic variation due to a very small population.  One of the common SNPs in this population is R183P. This is an arginine to proline change at position 183.

Lessons from John Burke's GeneEdit

John Burke does not have the mutation for this gene.