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Enzymes are essential for the proper functioning of all living organisms on Earth. They participate in most, if not all, chemical changes in nature, that is, in millions of reactions in both the plant world and the animal world. It is worth finding out what enzymes are, how they work and what their significance is for modern medicine.

Enzymesare protein molecules that accelerate or even allow various chemical reactions to take place in living organisms, including the human body.

From a chemical point of view, these are catalysts, i.e. particles that intensify the reaction, but do not wear out during the reaction. This increase in the efficiency of chemical transformations is often huge, natural catalysts can shorten the reaction time from several years to several seconds.

Enzymes are found in all areas of the body: in cells, in the extracellular space, in tissues, in organs and in their light, the catalysts a given tissue produces determines its specific properties and the role it plays in the body.

Most enzymes are very specific, which means that each of them is responsible for only one type of chemical reaction in which specific particles - substrates are involved, and only they can interact with a given enzyme.

The activity of natural catalysts depends on many factors: the reaction environment, e.g. temperature, pH, the presence of certain ions, activators - they enhance the action of enzymes and inhibitors that counteract this activity.

Enzymes: structure

As mentioned, most enzymes are proteins, they have a very diverse structure: from several dozen amino acids to several thousand arranged in a diverse spatial structure.

It is the form of their formation (the so-called quaternary structure) and the fact that most enzymes are much larger than the reactants of their reactions is largely responsible for their activity.

This is due to the fact that only a certain region in the structure of enzymes is the so-called active site, i.e. a fragment responsible for carrying out the reaction.

The task of the remaining fragments of the molecule is to attach a specific substrate, less often other compounds influencing the activity of the enzyme.

It's good to know that constructionof the catalyst is designed so that the joining substrate is ideally matched geometrically, like a "key to a lock".

Like all proteins, enzymes are produced in the ribosomes from the genetic material that is tightly packed in the nucleus - DNA, thus creating a so-called primary structure.

Then it undergoes folding several times - changing its shape, sometimes adding sugars, metal ions or fatty residues.

The result of all these processes is the formation of an active quaternary structure, i.e. a fully biologically active form.

In many cases, several enzyme particles combine to carry out a series of chemical reactions, and thus speed up the process.

Sometimes there are enzymes in several tissues that catalyze the same reaction, but are not structurally similar to each other, we call them isoenzymes.

The names of the isoenzymes are the same, despite the difference in location and structure, however, these differences have practical application. Thanks to this, it is possible to determine in laboratory tests only those fractions of the enzyme that come from a specific organ.

Enzymes' mechanisms of action are diverse, but from a chemical point of view, their task is always to lower the activation energy of the reaction. This is the amount of energy that the substrates must have for the process to take place.

This effect can be achieved by creating an appropriate environment for the reaction, using a different chemical route to obtain the same products, or the appropriate spatial arrangement of substrates.

Each of these mechanisms can be used by enzymes.

Regulation of enzyme activity

The action of enzymes depends on environmental parameters: temperature, pH and others. Each of the natural catalysts has its optimum performance under certain conditions, which may be differently wide depending on its tolerance to environmental conditions.

In the case of temperature, most enzymatic reactions are faster at higher temperatures, but at a certain temperature the reaction efficiency drops sharply, which is caused by thermal damage to the enzyme (denaturation).

In terms of their structure, hormones can be divided into two groups:

  • simple - only protein particles
  • complex - which require the addition of a non-protein group - a cofactor

The latter play a key role in the proper activity and regulation of enzymes.

Cofactors, in turn, can be divided into two groups: those necessary foractivities of the enzyme, strongly associated with it - these are so-called prosthetic groups, they can be metals, organic molecules, such as, for example, heme.

The second group are coenzymes, they are usually responsible for the transfer of substrates or electrons, and their binding to the enzyme is weak, this group includes, for example, folic acid, coenzyme A. It is worth knowing that many vitamins play the role of cofactors.

Inhibitors perform a completely different task, they are particles that inhibit enzymatic activity by binding to the enzyme.

There are several types of inhibitors:

  • irreversible - they cause permanent inactivation of the molecule and the reaction can only take place after the production of a new enzyme
  • competitive - in this case, the inhibitor has a structure similar to that of the substrate, so they compete for the active site. If an inhibitor is attached, the reaction does not occur, if the substrate - proceeds normally
  • non-competitive - such inhibitors bind the enzyme in a place other than that of the substrate, so it may attach to the enzyme, but the reaction does not take place

At a much higher concentration of the substrate than the inhibitor, the effect of the competitive inhibitor is overcome, because it overwhelms the "competition" for the active site, in the case of non-competitive, its effect cannot be overcome by increasing the concentration of the substrate.

In addition to the regulation of the activator and inhibitor systems, there are many other methods of controlling the activity of enzymes.

They concern the cell's control of production at the level of protein formation, as well as the regulation of the so-called post-translational processing, i.e. changes in the structure of a protein molecule occurring immediately after its synthesis in the ribosome. These modifications consist, for example, in shortening the polypeptide chain.

The next methods of regulation concern the segregation and placement of enzymes in appropriate areas: cellular and in specific organelles, or in the extracellular compartment.

There is one more important regulatory mechanism - negative feedback - it is the primary control system in the endocrine system. It works on the principle of inhibition.

This means that if an enzyme produces too much of a certain hormone, it binds to it, inhibiting its activity and reducing synthesis, so the reaction product itself inhibits its production.

Enzymes: role

Each tissue of the human body produces a specific set of enzymes, which defines the role of these cells in the functioning of the body. What are these enzymes is defined by the genetic code and which regions are active in a given cell.

Thousands of chemical reactions take place in the human body at any time, each of which requires a specific enzyme, so it would be difficult to list all these particles present in our body.

It is worth knowing about some of the most characteristic ones:

  • Digestive enzymes- produced by the tissues of the digestive system, they break down food into simple compounds, because only these can be absorbed into the blood. They are extracellular enzymes, so they fulfill their main task outside the cells in which they are produced. Some of these enzymes are formed in an inactive form, so-called proenzymes or zymogens, and are activated in the gastrointestinal tract. Digestive enzymes include, for example: amylase, lipase, trypsin.
  • Myosinis an enzyme found in muscles, it breaks down ATP molecules that are energy carriers, thus causing the muscle fibers to contract.
  • Peroxidasesare oxidizing enzymes and catalases, i.e. reducing enzymes
  • Acetylcholinesteraseis an enzyme that breaks down acetylcholine, one of the transmitters in the nervous system
  • Monoamine oxidaseis the enzyme most abundant in the liver, it is responsible for the breakdown of adrenaline, noradrenaline and some medications
  • Cytochomic oxidase , a very important intracellular enzyme responsible for energy transformations
  • Lysozym , a substance present e.g. in tears or saliva that fulfills protective functions, destroys pathogens
  • Alcohol dehydrogenase , an enzyme in the liver responsible for the breakdown of ethanol
  • Alkaline phosphatase , participates in bone building by osteoblasts

Enzymes: naming

Enzyme names are often quite complicated as they are derived from the name of the reaction they carry out and the substrate involved in that reaction, e.g. 5-hydroxytryptophan decarboxylase.

Typically, the suffix "-aza" is added to the general name of the reaction, and the second part of the enzyme name forms the name of the compound undergoing this reaction.

Sometimes the name is single, it comes from a substrate, e.g. lactase (an enzyme that breaks down lactose).

More rarely, the names of enzymes derive from a general process that takes place with their participation, e.g. DNA gyrase, the enzyme responsible for turning DNA strands.

Some enzymes finally have common names or names given by their discoverers, such as pepsin (which breaks down proteins in the digestive tract) or lysozyme (a bactericidal enzyme contained intears).

There is also a small group of restriction enzymes that are responsible for cutting DNA strands, in this case the name comes from the microorganism from which the enzyme was isolated.

The International Union of Biochemistry and Molecular Biology has introduced the rules for naming enzymes and divided them into several classes in order to standardize the nomenclature.

It did not replace the names described earlier, it is rather a supplement used primarily by scientists.

According to the rules of the European Union, each enzyme is described by a sequence of characters: EC x.xx.xx.xx - where the first digit stands for the class, subsequent subclasses and subclasses, and finally the enzyme number. These enzyme classes are:

• 1 - oxidoreductases: they catalyze oxidation and reduction reactions
• 2 - transferases: transfer functional groups (e.g. phosphate)
• 3 - hydrolases: correspond to the hydrolysis (decomposition) of bonds
• 4 - lyases: cut bonds in a different mechanism than hydrolysis
• 5 - isomerases: they are responsible for spatial changes of molecules
• 6 - ligases: connect molecules with covalent bonds

Enzymes and medicine

The importance of enzymes to human he alth is enormous. Their proper operation enables a he althy life, and thanks to the development of analytical devices, we have learned to diagnose various diseases by means of enzyme determination. What's more, we are able to successfully treat deficiencies of some enzymes and the resulting diseases, unfortunately, there is still a lot to do in this matter.

Treatment of the causes of metabolic diseases is not yet possible, because we are unable to safely and effectively modify the genetic material to repair damaged genes, and thus improperly produced enzymes.

Diseases resulting from dysfunctional enzymes

The proper functioning of our body depends largely on the proper functioning of enzymes. In many cases, disease states affect the amount of enzymes by causing them to be excessively released from cells or, on the contrary, deficient. Below are only examples of diseases caused by abnormal enzymatic functions, there are many more of these diseases.

  • Metabolic blocks or metabolic diseases

Metabolic blocks or metabolic diseases are a group of inherited diseases caused by the accumulation of substances in the cell due to the lack of an enzyme responsible for their metabolism. The substrates accumulated over time are so much that they become toxic to cells and the whole organism.

There are several thousand diseases, their number reflects the multiplicityenzymes found in the human body, as most enzyme-coding genes can be affected by metabolic diseases.

Examples are galactosemia or homocystinuria, which are rare diseases, most often manifested immediately after birth or in the first years of life.

  • Nowotwory

Another group of diseases that may involve malfunctioning of enzymes is cancer. In addition to many other functions, enzymes are also responsible for regulating cell division, so-called tyrosine kinases. If these enzymes fail in this area, uncontrolled cell division and therefore a cancerous process can occur.

  • Emphysema

A less common disease is emphysema, in which case elastase becomes overactive. It is an enzyme present in the lung tissue responsible for the breakdown of the elastin protein present, among others, in the lungs.

If it is too active, the balance between destroying and building is disturbed, scarring occurs and emphysema develops.

Enzymes: diagnostic use

Modern medical diagnostics is based on the use of enzymes in their determinations. This is due to the fact that disease states directly or indirectly lead to an imbalance of enzymes, causing increases or decreases in their amount in the blood.

This may result not only from production disorders, but also e.g. from the release of a large amount of intracellular enzyme into the blood or urine as a result of damage to its cell membrane.

Examples of enzymes used in laboratory research are:

  • Creatine kinase - an enzyme present in muscles, also in the heart muscle, its multiple increase may indicate a heart attack, myocarditis, muscle diseases - injuries, dystrophy.
  • Lactate dehydrogenase - present in all cells of the body, especially in the brain, lungs, white blood cells and muscles. Its large increase is observed in heart attacks, muscle and liver diseases or cancer.
  • Alkaline phosphatase is found in the greatest amount in the liver and bones, here it is released by osteoblasts. Diseases of these organs may cause its growth, but an excess of alkaline phosphatase may also indicate the bone regeneration process - after surgery or fracture.
  • Acid phosphatase occurs in many organs - liver, kidneys, bones, prostate, from the diagnostic point of view its increase may indicate bone and prostate diseases.
  • Aminotransferaseasparagine and alanine aminotransferase - these are enzymes characteristic of the liver, occurring almost exclusively in hepatocytes, they are used in the basic screening diagnosis of liver diseases, and their several-fold increases always encourage further diagnosis of liver diseases.
  • Glutamate dehydrogenase and gammaglutamyltransferase - other liver enzymes, similarly to those mentioned above, are important in the diagnosis of diseases of this organ and bile ducts.
  • Amylase is an enzyme present in many organs, but the highest concentration is achieved in the cells of the pancreas and salivary glands, its diagnosis is of greatest importance in their diseases.
  • Lipase is another pancreatic enzyme, it differs in specificity from amylase, which means that lipase is present only in the pancreas and deviations from the norm in the determination of this enzyme indicate pancreatic disease.
  • Cholinesterase is an enzyme that breaks down acetylcholine - a transmitter in the nervous system, where it is also present in the highest amount, in diagnostics it is used in poisoning with organophosphorus compounds.
  • Coagulation and fibrinolysis factors - these are substances produced by the liver involved in blood clotting, their determinations are important not only in the assessment of this process, but also in monitoring the liver function.
  • Alpha-fetoprotein - a liver enzyme, the amount of which increases in diseases of this organ, including cancer.
  • C-reactive protein - produced by the liver, involved in the immune response, its amount increases in the blood in inflammatory conditions - infections, injuries, autoimmune diseases.
  • Ceruloplasmin - another liver enzyme whose increase is characteristic of Wilson's disease.
  • Pyridinoline and deoxypyridinoline are markers of bone resorption (destruction), they characterize the function of osteoclasts (osteogenic cells).
  • Myoglobin - as mentioned earlier, it is a compound characteristic of muscles, so its increase will indicate damage to skeletal or cardiac muscles.
  • Troponins - so-called heart attack markers, these are enzymes that regulate the contraction of muscle fibers, they are especially abundant in the heart muscle. Its damage causes the release of large amounts of troponins into the blood, which is used in the diagnosis of heart diseases. It is worth remembering, however, that an increase in troponins may indicate not only a heart attack, but also its insufficiency, valve defects or pulmonary embolism.

All the enzymes listed above can be assigned to several groups:

  • secretory enzymes- the lower limit of the norm is diagnostic. These are enzymes physiologically produced by organs, but in the case of diseases their number decreases, e.g. clotting factors
  • indicator enzymes- growth is important. This group of enzymes appears in large numbers due to organ damage and enzyme leakage, such as troponins
  • excretory enzymes- these are enzymes produced normally into the lumen of various organs - the mouth, intestines and urinary tract. If their outlet is blocked, they get into the blood, e.g. amylase

It is worth remembering that enzymes are used in medical diagnostics itself. Biochemical analyzes are performed with the use of enzymes, and the appropriate interpretation of the results of enzymatic reactions allows to provide the result of a laboratory test.

Enzymes and treatment

Many drugs work by influencing the action of enzymes, either by causing their action to be stimulated or, on the contrary, by being inhibitors. There are enzyme substitutes such as pancreatin containing lipase and amylase used in pancreatic insufficiency.

On the other hand, certain groups of drugs inhibit the action of enzymes, e.g. angiotensin converting enzyme inhibitors used, among others, in hypertension and heart failure, or some antibiotics, e.g. amoxicillin, which inhibits the enzyme bacterial transpeptidase, which prevents the building of the bacterial cell wall, and as a result the infection is inhibited.

Some poisons also work by affecting enzymes. Cyanide is a potent inhibitor of cytochrome oxidase, an essential component of the respiratory chain. Blocking it prevents the cell from obtaining energy, which leads to its death.

For the proper course of the life processes of cells, it is necessary for the presence of many chemical substances, which remain in strict proportions among themselves and between which chemical reactions constantly occur.

This task is performed by properly functioning enzymes, which are necessary for almost any chemical reaction to take place with the speed and efficiency necessary for the proper functioning of the human body.

The action of enzymes accelerates these processes many times, often even hundreds of times, which is important, the enzymes themselves do not wear out during the reactions taking place.

The deficiency of catalysts or their improper operation may result in the emergence of many diseases. On the other hand, skillful modification of their activity allows you to successfully heal many ailments.

Enzymology (the science of enzymes) is extremely extensive, aits development may bring not only scientific progress, but also actively contribute to the development of medicine in terms of not only treatment, but also diagnostics.

About the authorBow. Maciej GrymuzaA graduate of the Faculty of Medicine at the Medical University of K. Marcinkowski in Poznań. He graduated from university with an over good result. Currently, he is a doctor in the field of cardiology and a doctoral student. He is particularly interested in invasive cardiology and implantable devices (stimulators).

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