Branched chain amino acids
Are normally completely catabolised by muscle to CO2 and H2O
Can be catabolised by liver but not muscle
Are the main dietary amino acids metabolized by intestine
Are a major source of nitrogen for alanine and glutamine produced in muscle
Alanine released from the muscle is the major substrate for gluconeogenesis (Fig. 9.29). Fig. 9.33. Hormonal regulation of gluconeogenesis i. Alanine is transpoed to liver, transaminated to pyruvate and conveed to glucose. This glucose may again enter the glycolytic pathway to form pyruvate, which in turn, can be transaminated to alanine. ii. Glucose-alanine cycle is impoant in conditions of starvation (Fig. 9.30). Thus net transfer of amino acid (nitrogen) from muscle to liver and corresponding transfer of glucose (energy) from liver to muscle is effected. iii. Alanine cycle is intimately related with Cori&;s cycleRef: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 105
Metabolism of protein and amino acid