Protein metabolism is a vital process in the human body. It is responsible for the uptake, buildup, breakdown, and removal of proteins. Proteins are the building blocks of human cells. If the metabolism does not run smoothly, a so-called metabolic disorder is present. The most common protein metabolism disorder in newborns is phenylketonuria.
What is protein metabolism?
Protein metabolism in the human body controls the absorption, buildup, breakdown, and excretion of proteins. Proteins, also called proteins, are made up of amino acids, such as lysine. Protein metabolism in the human body controls the uptake, build-up, breakdown as well as excretion of proteins. Proteins, also called proteins, are made up of amino acids. There are a total of 20 different amino acids. Eight of them are essential. This means that they must be taken in through food, since the organism cannot produce them itself. Protein metabolism is also called protein or amino acid metabolism. The body builds its cells, enzymes and hormones from proteins. Proteins can also serve as a source of energy.
Function and task
Along with fats and carbohydrates, proteins are an important main group of nutrients for the human body. Proteins are absorbed through food and broken down in the stomach by the enzyme pepsin to form polypeptides and oligopeptides. In regular spurts, these substances are released into the small intestine. In this organ, the peptides are further broken down by the enzyme trypsin to chymotrypsin. In this form, the broken-down nutrient is available. As amino acids, the proteins enter the small intestine and are absorbed through its wall. The remaining amino acids, which are not absorbed, are broken down in the body or used for the production of the body’s own proteins, for example enzymes. For this purpose, it is important that all relevant amino acids are available in sufficient quantities. If only one amino acid is missing, the production of the body building blocks that require this amino acid cannot continue. There are 20 amino acids. The organism can produce twelve of them itself. The remaining eight amino acids cannot be produced by the human body. These are essential and must be taken in through food. The organism needs proteins for growth and repair processes. Proteins are the building blocks of all human cells. Protein is needed to form new cells or to repair damaged cells. Since protein stores in the body are limited, this nutrient must be obtained through regular consumption of protein-rich foods. Enzymes and hormones are also built from amino acids. The building of these proteins takes place largely in the liver. However, regular building of proteins from amino acids also takes place in all other cells. If there is a nutrient deficiency, proteins can also serve to generate energy for the body in addition to carbohydrates and fats. For this purpose, proteins from the spleen, muscles and liver are converted to pyruvate. This substrate can be used directly as an energy source or indirectly converted to glucose through another metabolic process. This process produces ammonia, which is toxic to the organism. A small part of it is excreted directly by the kidneys. The rest is converted to urea in the liver and excreted in the urine.
Diseases and ailments
For metabolism to occur properly, substances needed for it must be available and various enzymes must work together. If individual parts of the process are defective because a particular enzyme is not present, metabolism cannot function smoothly. An enzyme defect can therefore be the cause of a metabolic disease. The body then lacks certain enzymes, and substances are produced or stored in excessive numbers. This can be caused by genetic factors or an unhealthy lifestyle. The most common metabolic disorder in infants in protein metabolism is the so-called phenylketonuria. The cause of the disease is an enzyme defect, whereby the amino acid phenylalanine is not converted to tyrosine. Phenylalanine cannot be broken down in the body and accumulates in the brain of the affected person. If left untreated, patients suffer irreparable damage to the brain. This impairs motor and mental development. Furthermore, too little tyrosine is available.This amino acid is needed for the formation of various hormones. The only effective therapy is a diet with foods low in phenylalanine. Especially until the age of 12, a diet of low-protein foods such as meat, eggs, milk, and cheese is recommended, as the brain fully develops during these years of life. However, it is advisable to avoid high-protein foods for life with this condition. Since phenylketonuria is relatively common, every newborn is tested for this disorder. Another protein metabolism disorder is amyloidosis. In this disorder, so-called amyloid accumulates around body cells. Compared to other proteins produced by the body, amyloid has an abnormal structure. As a result, it cannot be broken down and attaches itself to one or more organs. Deposits on oranges can lead to impaired functioning of them. All organs of the human body can be affected. Certain underlying diseases can favor the occurrence of this disorder. In this case, the underlying disease must be treated. Amyloidoses that do not cause any symptoms are also possible. These usually do not need to be treated. Whereas amyloidoses with organ-related disease symptoms, such as heart failure caused by deposits on the heart muscle, require symptomatic treatment. The cause of amyloidosis is still largely unclear.
