A delicate balance exists between digestion of proteins and removal of urea from the body. Protein energizes the body at the price of toxic waste build-up. This waste must be removed for optimum health. The liver and kidneys play a crucial role in removing waste products. Certain disease processes can disturb this delicate balance.
Proteins ingested as amino acids in food convert to carbon and hydrogen used for energy. The remainder converts to ammonia, a toxic waste product, reports Harvard Health Publications. The conversion process is known as deamination. The liver detoxifies the body of ammonia, utilizing five enzymes which turn unwanted ammonia into urea. The bloodstream carries urea from the liver to filtration by the kidneys. Urea is eliminated from the body in urine.
Breakdown of Ammonia
Enzymes convert ammonia, a nitrogen compound, to urea or uric acid in the liver by adding carbon dioxide molecules, reports Professor Silva. The conversion to urea also takes place in part in the kidneys. The breakdown of proteins converts to urea. The breakdown of nucleic acids converts to uric acid. The renal corpuscle acts to filter cells and proteins into ultrafiltrate, which becomes urine. Urea and uric acid are less toxic than ammonia, states Silva.
Ornithine, although an amino acid, is not part of the genetic code and is not involved in protein synthesis. Ornithine, however, plays a crucial role in the conversion of ammonia to urea. Elmhurst College states the urea cycle in the liver produces bonds between two amino groups, one molecule of carbon dioxide and ornithine. The cycle is replenished as urea is produced from this bond and ornithine is released to produce more urea, states the University of South Australia.
Proteins Aid in Fluid Removal
A blood protein known as albumin draws extra fluid from the body into the bloodstream, states the National Kidney and Urologic Diseases Information Clearinghouse, or NKUDIC. The fluid is eventually removed from the blood by the glomeruli--the kidney's filtration system. The NKUDIC states that albumin works like a sponge to remove excess fluid, which can cause swelling in areas such as the ankles and feet, hands and face.
Protein in Urine
The glomerular membrane of the kidney filters blood, allowing waste products and extra water to pass through while blocking proteins and cells, states NKUDIC. Certain diseases of the kidney, known as glomerular diseases, allow albumin from the blood to leak through the membrane into the urine. Large amounts of protein in the urine is a condition called proteinuria, reports NKUDIC. Hypoproteinemia refers to low blood protein.
Conditions Causing Proteinuria
The NKUDIC reports there are a number of conditions that may cause glomerular disease. Infection, toxic drugs or systemic diseases such as diabetes or lupus may cause glomerular disease. There may also be unknown causes of glomerular disease, states the NKUDIC.
Genetic Protein Disorder
Lysinuric protein intolerance is a genetic disease that causes protein imbalance, states the National Library of Medicine. This disorder causes an inability to digest the amino acids lysine, arginine and ornithine. An enlarged spleen and liver develop with muscle weakness and brittle bones. Protein deposits may fill the lungs. A build-up of amino acids occurs in the kidneys with resultant kidney failure. A lack of amino acids in the blood causes too much ammonia to build up in the blood. The untreated condition will result in coma.
- University of South Australia: Protein Metabolism
- Harvard Health Publications: Urea Cycle Disorder and Protein Metabolism
- Prof. Doutor Pedro Silva: The Chemical Logic Behind Aminoacid Degradation and Urea Cycle
- NKUDIC: Glomerular Diseases
- U.S. National Library of Medicine: Genetics Home Reference
- Elmhurst College: Urea Cycle