there is controversy concerning the origin of the carbon skeleton of alanine produced in muscle , specifically whether it is derived from carbohydrate via glycolysis ( the glucose-alanine cycle ) or from amino acid precursors ( viz . glutamate , valine , isoleucine , methionine , aspartate , asparagine ) via a pathway involving phosphoenolpyruvate ( pep ) carboxykinase and pyruvate kinase , or nadp-malate dehydrogenase ( malic enzyme ) .
C0001898
alanine
C0002520
amino acid