Food Chemistry and Fish in Nutrition

8.1.2.Metabolism

Metabolism

            The amino acids entering the liver, following absorption from the intestinal tract, also have several important metabolic routes.

 

i). Transport to other tissues: Amino acids may pass into the systemic blood and thus to other organs, to be used as building block in the biosynthesis of tissue proteins.

 

ii) Biosynthesis of liver proteins and plasma proteins: The liver constantly renews its own intrinsic proteins, which have a very high turnover rate. The liver is also the site of biosynthesis of most of the plasma proteins of the blood.

 

iii) Deamination and degradation: Amino acids which not needed for protein biosynthesis in the liver or other tissues are deaminated and degraded to yield acetyl CoA and citric  acid  cycle intermediates. Citric acid cycle inter mediates thus  formed may be converted into blood glucose  and glycogen  via the glyconeogenesis pathway.

 

iv) Participation in the glucose – Alanine cycle: The liver also  participates in the metabolism of amino acids arriving from other tissues. These amino acids are  deaminated and the resulting keto acids are converted into blood glucose via  gluconeogenesis. The NH3 is converted into urea for excretion.

 

v) Conversion into Nucleotides and other Products:  Amino acids are precursors in the biosynthesis of the purine and pyrimidine bases of the nucleotides and in the synthesis of specialized products such as porphyrins, hormones and other nitrogenous compounds.