In maple syrup disease, all of the following amino acids are excreted in urine, EXCEPT:
The biochemical defect in maple syrup urine disease (branched-chain ketonuria, or MSUD) involves the alpha-keto acid decarboxylase complex. Plasma and urinary levels of leucine, isoleucine, valine, and their alpha-keto acids and alpha-hydroxy acids (reduced alpha-keto acids) are elevated, but the urinary keto acids derive principally from leucine. Signs and symptoms of MSUD include often fatal ketoacidosis, neurological derangements, mental retardation, and a maple syrup odor of urine. Ref: Rodwell V.W. (2011). Chapter 29. Catabolism of the Carbon Skeletons of Amino Acids. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.
Valine
Leucine
Isoleucine
Phenylalanine