Question

What is the interplay between pyruvate and alanine in terms of transporting NH₃ from the muscle tissue to the liver?

Answer 1

THE DOMINENT REACTIONS INVOLVED IN REMOVING AMINOACID NITROGEN FROM THE BODY ARE KNOWN AS TRANSAMINATIONS .THIS CLASS OF REACTIONS FUNNELS NITROGEN FROM ALL FREE AMINOACIDS IN TO A SMALL NUMBER OF COMPOUNDS , THEN EITHER THEY ARE OXIDATIVELY DEAMINATED PRODUCING AMMONIA OR THEIR AMINE GROUP ARE CONVERTED TO UREA BY UREA CYCLE . TRANSAMINATION REACTIONS ARE CATALYZED BY A GROUP OF INTRACELLULAR ENZYME KNOWN AS AMINOTRANSFERASES , ALT OR ALANINE TRANSAMINASE IS AN ENZYME LIKE THIS . IT HAS AN IMPORTANT FUNCTION IN THE DELIVERY OF SKELTAL MUSCLE CARBON AND NITROGEN IN THE FORM OF ALANINE TO THE LIVER IN A SERIES OF REACTION REFERED TO AS GLUCOSE ALANINCYCLE

IN SKELTAL MUSCLE GLUCOSE UNDERGO GLYCOLYSIS PRODUCE PYRUVATE . PYRUVATE IS TRANSAMINATED IN TO ALANINE, AFFORDING AN ADDITIONAL ROUTE FOR NITROGEN TRANSPORT FROM MUSCLE TO LIVER . IN THE LIVER ALANINE TRANSAMINASE TRANSFERS THE AMMONIA TO 2 OXO GLUTARATE AND REGENERATE PYRUVATE. THE PYRUVATE DIVERTED IN TO GLUCONEOGENESIS ALLOWING THE LIVER TO GENERATE ENDOGENOUS GLUCOSE WHICH THEN RELEASE TO THE BLOOD WHERE SKELTAL MUSCLE CAN USE IT FOR ANAEROBIC ENERGY PRODUCTION. THE AMINO GROUP TRANSPORTED FROM THE MUSCLE TO THE LIVER IN THE FORM OF ALANIN IS CONVERTED TO UREA IN THE UREA CYCLE AND EXCREATED THUS GLUCOSE ALANINE CYCLE IS USED PRIMARLY AS A MECHANISM FOR SKELTAL MUSCLE TO ELIMINATE NITROGEN WHILE REPLENISHING ITS ENERGY SUPPLY