The carbon skeletons of Methionine, Isoleucine, Threonine and Valine are degraded by pathways that yield Succinyl-CoA (Succinyl-Coenzyme A), an intermediate of the Citric Acid Cycle. Methionine donates its Methyl group to one of several possible acceptors through S-adenosylmethionine and three of its four remaining carbon atoms are converted to the Propionate of Propionyl-CoA, a precursor of Succinyl-CoA. Isoleucine undergoes transamination, followed by oxidative decarboxylation of the resulting Alpha-Keto Acid. The remaining five-carbon skeleton is further oxidized to Acetyl-CoA and Propionyl-CoA. Valine undergoes transamination and decarboxylation and then a series of oxidation reactions convert the remaining four carbons to Propionyl-CoA (Ref.1). In human tissues, Threonine is also converted in two steps to Propionyl-CoA. This is the primary pathway for Threonine degradation [...]