Cytosolic glutamic-pyruvate transaminase (alanine aminotransferase) (GPT) catalyzes the reversible reaction of pyruvate and glutamate to form alanine and 2-oxoglutarate (alpha-ketoglutarate) (Sohocki et al. 1997; Yang et al. 2002). The active form of the enzyme is a dimer (Ishiguro et al. 1991) and is inferred to have a molecule of pyridoxal phosphate associated with each monomer. This reaction allows the synthesis of alanine from intermediates of glucose metabolism in a well-fed person. Under fasting conditions, alanine, derived from protein breakdown, can be converted to pyruvate and used to synthesize glucose via the gluconeogenic pathway in liver, or fully oxidized via the TCA cycle in other tissues.