description
General Background : LEU is one of the three main branched chain amino acids (BCAAs), along with : ILE and :VAL. The catabolic pathways of the BCAAs can be divided into two sequential series of reactions, referred to as the common pathway and the distal pathway. The distal parts of the pathways are completely different for the three BCAAs, and comprise enzymes specific for each amino acid . About this Pathway The catabolism of : LEU begins with its transamination to : 2K-4CH3-PENTANOATE, followed by oxidative decarboxylation to : ISOVALERYL-COA. The : ISOVALERYL-COA then undergoes a four-step process, involving dehydrogenation to : 3-METHYL-CROTONYL-COA, carboxylation to : TRANS-3-METHYL-GLUTACONYL-COA, hydration to : 3-HYDROXY-3-METHYL-GLUTARYL-COA and finally a thioester hydrolysis forming : ACETYL-COA and :3-KETOBUTYRATE . The catabolism of leucine differs from the catabolism of the other branched-chain amino acids, in that it includes a carboxylation step. The : CARBON-DIOXIDE fixing enzyme : CPLX66-17, requires biotin as a cofactor. In adipocytes, leucine is a significant precursor for fatty acid and sterol biosynthesis, especially in the presence of glucose . Furthermore, leucine can serve as a source of nitrogen for the synthesis of : GLN and to a lesser extent : GLT and : L-ALPHA-ALANINE, which are released by adipocytes and serve as substrates for gluconeogenesis in liver and kidney

external resources
NCBI:142359
BIOCYC:HUMAN_LEU-DEG2-PWY
PUBMED:13892210
PUBMED:6773935
PUBMED:773366
PUBMED:6304077
PUBMED:4150714

genes
AUH , BCAT1 , BCAT2 , BCKDHA , BCKDHB , DBT , DLD , HMGCL , IVD , HMGCLL1 , MCCC1 , MCCC2 ,