During vigorous strenuous exercise, which of the following amino acid is liberated from the skeletal muscles in maximum amount into circulation

Answer: d) AlanineALANINE* Alanine is a non-essential glucogenic amino acid.* Alanine can be formed by transamination of pyruvate.* The enzyme is alanine amino transferase (ALT).* Pyruvate + Glutamate - Alanine + alpha ketoglutarate* This reaction requires pyridoxal phosphate (PLP).* Under conditions of starvation, the glucose alanine cycle is of special metabolic significance.* Alanine is quantitatively the most important amino acid taken up by the liver from peripheral tissues, particularly from skeletal muscle.* It forms a major participant in inter-organ transport of nitrogen Glucose-Alanine Cycle (Cahill Cycle)* Alanine is transported to liver, transaminated to pyruvate and converted to glucose.* This glucose may again enter the glycolytic pathway to form pyruvate, which in turn, can be transaminated to alanine.* Glucose-alanine cycle is important in conditions of starvation.* Thus net transfer of amino acid (nitrogen) from muscle to liver and corresponding transfer of glucose (energy) from liver to muscle is effected.* Alanine cycle is intimately related with Cori's cycleAmino AcidArterial Concentration Rest240 min Exercise mmol/l Glycine188160Alanine192233Leucine126151!Valine242243Isoleucine6081!