Intermediate metabolism

Of the Intermediate metabolism is also known as Intermediate metabolism designated. This concerns all metabolic processes at the interface between anabolic and catabolic metabolism. Disturbances of the intermediate metabolic processes are mostly due to enzymatic defects and mainly manifest themselves as storage diseases.

What is the intermediate metabolism?

Metabolism (also called metabolism) is divided by medicine into the areas of anabolism and catabolism. Anabolism is used to build chemical compounds. Catabolimus is used to break down the same. A third metabolic reaction is that Amphibolism. This term is associated with intermediate metabolism.

Metabolic reactions of the intermediate metabolism relate to metabolites with a molecular mass below 1000 g / mol. These metabolites are converted into one another in the reactions of the intermediate metabolism. Depending on requirements, the intermediate metabolism draws metabolites from catabolism or anabolism for this purpose. Unlike these two terms of metabolism, the intermediate metabolism is neither associated with a specific breakdown nor build-up. Amphibolism can have both catabolic and anabolic effects.

Ultimately, the intermediate metabolism comprises all metabolic reactions that take place at the individual interfaces between anabolism and catabolism. Catabolism corresponds to a largely oxidative breakdown of large molecules (carbohydrates, fats, proteins) and anabolism is the enzymatic synthesis of molecular cell components.

Function & task

Catabolism breaks down large molecules of food into smaller molecules in order to release energy and to conserve it in the form of high-energy phosphate bonds as adenosine triphosphate. Catabolism has three main stages. Level 1 corresponds to breaking down large nutrient molecules into individual building blocks. For example, polysaccharides become hexoses and pentoses. Fats turn into fatty acids and glycerin. Proteins are broken down into individual amino acids. Stage 2 corresponds to the conversion of all molecules created in stage 1 into simpler molecules. At stage 3, the products from stage 2 are transferred to final degradation and thus to oxidation. The result of this stage is carbon dioxide and water.

Anabolism mainly corresponds to a synthesis process that results in more complex and larger structures. As size and complexity increase, there is an entropic decrease. Anabolism is dependent on the supply of free energy, which it withdraws from the phosphate bonds of ATP. Like catabolism, anabolism occurs in three stages. In the first stage he uses the small building blocks of catabolic stage 3. Stage 3 of catabolism is thus at the same time stage 1 of anabolism. The catabolic and anabolic metabolic pathways are not identical, but have catabolic level 3 as a connecting and central element. This stage therefore represents a common metabolic step.

The common central path of catabolism and anabolism is amphibolism. This central pathway has a double function and can catabolically result in the complete breakdown of the molecules as well as make smaller molecules available anabolically as starting materials for the synthesis process. Catabolism and anabolism are therefore based on mutually dependent processes.

The first of these processes are the successive enzymatic reactions that lead to the build-up and breakdown of biomolecules. The chemical intermediates from this process are called metabolites. The processing of substances into metabolites corresponds to the intermediate metabolism. The second process characterizes every single reaction of the intermediate metabolism and corresponds to an energy exchange. This is an energy coupling. In certain processes of the catabolic reaction sequence, chemical energy is conserved by converting it into energy-rich phosphate bonds. Certain reactions in the anabolic metabolic sequence ultimately draw this energy.

Illnesses & ailments

The entire metabolism offers a multitude of starting points for certain diseases. Disturbances of the intermediate metabolism can have fatal and even life-threatening consequences. This applies, for example, when, as part of intermediate metabolism, toxic metabolites are stored in vital organs and these organs are impaired in their function. Such disorders of the intermediate metabolism are often associated with mutations that lead to a deficiency or malfunction of certain metabolic enzymes. An imbalance between supply and demand for certain chemical substances can also lead to disorders of the intermediate metabolism.

Intermediate metabolic disorders caused by mutations are, for example, glycogen storage diseases. This group of diseases leads to the storage of glycogen in various body tissues. A conversion to glucose is hardly or not at all possible for the patients of these diseases. The cause is a mutation-related defect in enzymes that break down glycogen. Glycogen storage diseases due to enzyme defects include, for example, von Gierke's disease, Pompe disease, Cori disease, Andersen's disease, and McArdle's disease. Hers and Tarui's disease also fall into this group of diseases.

The defects can affect various metabolic enzymes, such as glucose-6-phosphatase, alpha-1,4-glucosidase and amylo-1,6-glucosidase, for example alpha-1,4-glucan-6-glycosyltransferase, alpha-glucan phosphorylase or alpha-glucan phosphorylase and phosphofructokinase.

Storage diseases caused by disorders of the intermediate metabolism do not necessarily have to be glycogenoses, but can also correspond to mucopolysaccharidoses, lipidoses, sphingolipidoses, hemochromatosis or amyloidoses. With lipidoses, lipids accumulate in cells. In the context of amyloidoses, insoluble protein fibrils are deposited intracellularly and extracellularly. Hemochromatosis is characterized by abnormal deposition of iron and sphingolipidoses are based on lysosomal enzyme defects that cause sphingolipid accumulation. The effects of a storage disease mainly depend on the stored substance and tissue.