Food Chemistry and Fish in Nutrition

8.1.3.Dynamic state of protein or Constant turnover of proteins

Dynamic state of protein or Constant turnover of proteins

            Proteins are in a constant state of degradation and resynthesis. All body proteins continuously undergo degradation and synthesis. More than half of the protein in liver and intestinal mucosa are broken down and resynthesised in 10days. Active resynthesis occurs even in starvation and active breakdown in nitrogen equilibrium. Degradation of protein in one tissue is accompanied by systhesis in others. When amino acids are oxidized, their nitrogen atoms are fed into the urea cycle in the liver and excreted as urea in the urine, sweat and feces. Other nitrogenous excretory products include uric acid, creatinine and ammonia.

 

The continuous turnover of protein in the adult is probably necessary for maintaining an amino acid pool, and the capability to meet the demand for amino acids by various cells and tissues when they are stimulated to make necessary proteins. The most active tissues for protein turnover are the plasma proteins, intestinal mucosa, pancreas, liver, and kidney whereas the muscle, skin, and brain are much less active