Which of the following transpos nitrogen from muscle to liver?
Glucogenic amino acids i. Glucogenic amino acids are shown in Figure 9.27. (Alanine, glutamic acid, aspaic acid, etc). ii. When glucose is not readily available (starvation or diabetes mellitus), the glucogenic amino acids are transaminated to corresponding carbon skeletons. (Fig. 9.27). These then enter the TCA cycle and form oxaloacetate or pyruvate. iii. 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
Lactate
Alanine
Glutamine
Aspeate
Metabolism of protein and amino acid