Enzymes - a globular proteins that help to flow all cellular processes.Like all catalysts, they can not turn back the response and serve to accelerate it.
localization of the enzyme in the cell
individual enzymes inside cells, normally found and operate in a strictly defined organelles.Localization of enzymes directly related to the function which usually performs this portion of the cell.
Almost all the enzymes of glycolysis are located in the cytoplasm.Enzymes Krebs cycle - in the mitochondrial matrix.The active substances contained in the lysosomal hydrolysis.
Selected tissues and organs of animals and plants are distinguished not only by a set of enzymes, but also by their activity.This feature fabrics used clinically in the diagnosis of certain diseases.
There are also age-specific features in the activity of enzymes and set in the tissues.They are most clearly visible in the period of embryonic development when tissue differentiation.
Enzyme Nomenclature
There are several systems of names, each of which takes into account the properties of the enzyme to varying degrees.
- trivial.The names of the substances are randomly featured.For example, pepsin (pepsis - "digestion", Gk.) And trypsin (tripsis - "dilutes" the Greek.)
- rational.The name of the enzyme is composed of the substrate and the end of "-aza."For example, amylase accelerates starch hydrolysis (amylo - "starch", Gk.).
- Moscow.It was adopted in 1961 by the International Commission on the nomenclature of enzymes at the V International Biochemical Congress.Title substance is composed of a substrate and the reaction is catalyzed (accelerated) by the enzyme.If the enzyme is to carry a group of atoms from one molecule (substrate) to another (the acceptor), the name of the catalyst includes the chemical name acceptor.For example, in the transfer reaction of the amino group from alanine to 2-oksiglutarovuyu acid participates enzyme alanine: 2-oksoglutarataminotransferaza.The name reflects:
- substrate - alanine;
- acceptor - 2-oxoglutaric acid;
- amino group transfer reaction.
International Commission has compiled a list of all known enzymes, which is constantly updated.This is due to the discovery of new materials.
Classification of enzymes
Share enzymes into groups in two ways.The first offers two classes of substances:
- simple - composed only of protein;
- complex - containing protein part (apoenzyme) and non-protein called coenzyme.
The non-protein part of a complex enzyme may include vitamins.Interaction with other substances occurs through the active site.Total enzyme molecule is not involved in the process.
properties of the enzyme, as well as other proteins are determined by their structure.In dependence thereon only catalysts accelerate their reaction.
second way classification divides the substance to what function is performed by enzymes.The result is six classes:
- oxidoreductase;
- transferase;
- hydrolase;
- isomerase;
- lyase;
- ligase.
This conventional group, they differ not only by types of reactions that regulate them consisting enzymes.In substances of different groups of different structure.And the function of enzymes in the cell, therefore, can not be the same.
Oxidoreductases - redox
The main function of the enzymes of the first group - the acceleration of redox reactions.A characteristic feature: the ability to form a chain of oxidative enzymes, in which the transfer of electrons or hydrogen atoms from the first substrate to a final acceptor.These substances are separated on the principle of operation or at work in the reaction.
- Aerobic dehydrogenase (oxidase) accelerate the transfer of electrons or protons directly to oxygen atoms.Anaerobic also perform the same steps, but in the reactions that take place without the transfer of electrons or hydrogen atoms to oxygen atoms.
- primary dehydrogenases catalyze the process of withdrawal of the hydrogen atoms of the substance to be oxidized (the primary substrate).Secondary - accelerate the removal of hydrogen atoms from the secondary substrate, were obtained by means of the primary dehydrogenase.
Other features: as a two-component catalyst with a very limited set of coenzyme (active groups), they can accelerate the set of a variety of redox reactions.This is achieved by a large number of variants: the same coenzyme may adhere to different apofermentami.In each case, a special oxidoreductase with its properties.
There is another feature of this group of enzymes, which can not mention - they accelerate the chemical processes associated with the release of energy.Such reactions are called exothermic.
Transferases - carriers
These enzymes carry out the function of accelerating the transfer of molecular reactions residues and functional groups.For example, phosphofructokinase.
There are eight groups of catalysts, based on the group tolerated.Consider just some of them.
- phosphotransferase - help to transfer the remains of phosphoric acid.They are divided into subclasses according to the destination (alcohol, carboxylic acid, etc.).
- Aminotransferases - accelerate the reaction of transamination of amino acids.
- glycosyltransferase - transferred glycosyl residues from molecules to molecules of phosphoric esters of mono- and polysaccharides.Provide decomposition reactions and synthesis of oligosaccharides or polysaccharides in plant and animal organisms.For example, they participate in decomposition reactions of sucrose.
- acyltransferase carry carboxylic acid groups to amines, alcohols and amino acids.Acyl-coenzyme-A is a versatile source of acyl groups.It can be considered as an active group acyltransferases.Most often tolerated acyl acetic acid.
Hydrolases - cleaved with water
In this group of enzymes function as catalysts for the cleavage reactions (synthesis less) of organic compounds in which water is involved.Substances of this group contained in the cells and in the digestive juice.The molecules in the gastrointestinal tract catalysts consist of a single component.
place of localization of these enzymes are lysosomes.They serve protective functions of enzymes in the cell: cleave foreign substances pass through the membrane.They also consume those substances which are no longer needed cell lysosomes for which nurses were dubbed.Other
their "nickname" - cell suicide, as they are the main tool for cell autolysis.If there was an infection, inflammatory processes have begun, the membrane becomes permeable and lysosomal hydrolases are located in the cytoplasm, destroying everything in its path and destroying the cell.
Separate multiple types of catalysts from this group:
- esterase - are responsible for the hydrolysis of esters, alcohols;
- glycosidase - accelerate hydrolysis of glycosides, depending on which isomer they operate, emit α- or β-glucosidase;
- peptide hydrolase - are responsible for the hydrolysis of peptide bonds in proteins and, under certain conditions, and their synthesis, but this method is not used in protein synthesis in living cells;
- amidase - responsible for the hydrolysis of amides, for example, urease catalyzes the decomposition of urea into ammonia and water.
Isomerases - converting molecules
These substances accelerate changes within a single molecule.They may be structural or geometric.This can happen in different ways:
- transfer of hydrogen atoms;
- movement of a phosphate group;
- change the location of atomic groups in space;
- displacement of the double bond.
isomerization may be exposed to organic acids, carbohydrates and amino acids.Isomerase can convert aldehydes and ketones, in contrast, the cis-form transformed into trans form and vice versa.To better understand what function is performed by the enzymes of this group, you need to know the differences isomers.
Lyases tear due
These non-hydrolytic enzymes accelerate the decomposition of organic compounds Relations:
- carbon-carbon;
- phosphorus-oxygen;
- carbon-sulfur;
- carbon-nitrogen;
- carbon-oxygen.
This includes such simple products, such as carbon dioxide, water, ammonia, and closed the double bonds.Few of these reactions can go in the opposite direction, corresponding to the enzymes under suitable conditions for this process not only catalyze the decomposition and synthesis.
lyases classification occurs according to the type of communication, which they break.They are complex enzymes.
Ligases crosslinked
The main function of the enzymes of this group - the acceleration of fusion reactions.Their feature - Pair creation with the collapse of the substances, which are able to provide energy for biosynthetic processes.There are six subclasses type connection formed.Five of them are identical subgroups lyase, and the sixth is responsible for creating communication "nitrogen-metal".
Some ligases are involved in particularly important processes of the cell.For example, a DNA ligase involved in the replication of deoxyribonucleic acid.She sews nicked, creating new phosphodiester bonds.It was she who joins Okazaki fragments.
This same enzyme is widely used in genetic engineering.It allows scientists to crosslink the DNA molecule of the pieces they need, creating a unique chain of deoxyribonucleic acid.They can lay any information, thus creating a factory for the production of essential proteins.For example, it is possible to sew a piece of bacterial DNA which is responsible for the insulin synthesis.And when a cell own proteins will broadcast it at the same time let us make and minerals needed for medical purposes.It remains only to clear, and it will help many sick people.
huge role of enzymes in the body
They can increase the reaction rate more than ten times.It is essential for normal cell activity.A enzymes participate in each reaction.Therefore, the function of enzymes in the body are varied, like all occurring processes.A disruption of these catalysts leads to serious consequences.
enzymes are widely used in food processing, light industry, medicine: used to make cheese, sausages, canned food, are part of the laundry detergent.They are also used in the manufacture of photographic materials.
