As mentioned above, digestion is possible thanks to catalytic protein, the so-called Enzymes. These molecules start the processes taking place in the body. Enzymes are responsible for maintaining the homeostasis of the body and the disorder of their work causes the development of various diseases, an example of which may be, for example, the lack of lactase causes gastrointestinal discomfort after consumption of products with sugar – lactose.
Enzymes build proteins and proteids. However, usually these are the latter – complex proteins (such a protein consists of a protein part and a non-protein part, e.g. a vitamin).
The non-protein part can bind permanently with the enzyme and temporarily (during the reaction). If the connection is permanent then the non-protein part is called a prosthetic group, if the connection is not permanent then it is a coenzyme. With complex proteins, the protein part is called apoenzyme and the whole enzyme (connected with epoenzyme with a prosthetic group or coenzyme) is a holoenzyme.
Parts of non-protein enzymes attached / lurk to the so-called Active center. In these places a substrate is also connected, which is subject to the given process Fig.1. The active center makes up the side chains of protein amino acids, they are often called “catalytic groups of the enzyme – they are responsible for the dissolution, attachment, processing and determine the properties of the enzyme. The conclusion from the previous sentence is that the enzymes are specific. A given enzyme processes a given substrate (see the inductive fit model, the “key and lock model”).
Key and lock model
The method of imaging enzyme work in this way assumes that the substrate completely fits into the active center as a “key to the lock. However, due to the fact that it was shown that such a combination would not be able to reduce the activation energy so much, a second method was created.
The model of the indicative adjustment
Very good translation of this model, which I found 1, here’s a quote
“It assumes that in fact the conformation (spatial designer) of the substrate and the active center are not identical. At the time of formation of enzyme-substrate complexes, Fig. 1, a specific “substrate pull into the active site occurs, which is accompanied by a slight stress of bonds in both components of the ES complex. In this situation, a small portion of energy is enough to overcome the energy threshold of reaction. The fact that the bond changes only in the substrate, is usually explained by the size of the enzyme molecule.2 – a higher mass affects the stability and less susceptibility to deformation. Sometimes, therefore, for a pictorial explanation of the inductive fit mode, it is said that the substrate fits into the active center like a gloved hand.
Factors affecting the work of enzymes
The main impact on the work of these proteins is mainly the temperature of the environment in which they work and its pH.
1) Environmental PH
Enzymes have a specific range of action. This is their optimal value. Significant deviation, i.e. too large a change in pH, can inhibit the enzyme, e.g. by denaturing, while a slight deviation can affect the rate of reaction.
Denaturation of the enzyme is due to the fact that in the acidic medium there are more H + hydrogen cations than the OH- anions. The former then affect the dissociating (amine and carboxyl) groups present in amino acid residues of the peptide chains, mainly in the vicinity of the active site. The degree of dissociation changes, and in the pair to change, there are 3 protein structures under construction, which can reduce activity, or lead to complete disruption of structures and completely inhibit its work.
The pH optimum for enzymes is 5-8, however, for some ph values in which they work are strongly acidic or more strongly alkaline. Pepsin in the stomach, where ph is low by hydrochloric acid, works optimally at pH 1.8; trypsin, at 8-11.
In our body, acidification of the body caused mainly by eating too much protein (acid-forming) / too small amount of vegetables (alkaloid) causes a decrease in enzyme function and during de-acidification their activity returns to normal, which is noticed eg by increased thermogenesis. The body must maintain the appropriate ph environment in different parts of the body, otherwise the pH values would fluctuate, which would negatively affect the work of enzymes.
2) Environmental temperature
It is clear that increasing the temperature of the environment affects the acceleration of collisions of particles or ions, and thus leads to acceleration of the reaction. Increasing the reaction by 10 degrees C already 2-3 times accelerating the course of the reaction, but such a high temperature increase would denature the enzyme and ultimately inhibit the enzyme activity, stop the workflow. The optimal temperature for animal enzymes (including us) is the bilin value of the optimal body temperature.
3) Inhibitors and activators
Enzymes may be inactive, and their activation is influenced by a given substance. Inactive enzymes are called proenzymes, blocking them is related to the placement of the inhibitor (enzyme blocking compound) in the active center of the enzyme.
Proenzymes have the suffix -ogen whereas the enzymes -aza, -for example trypsinogen – trypsin.
Enzyme inhibitors can be drugs, poisons. Abnormal enzymatic work of the body can lead to the development of diseases and for this purpose, for example, you can use the appropriate drugs that can be used as enzyme inhibitors or act as stimulants of their work – activators.
4) Concentration of the substrate relative to the enzyme
Michaelis Menten theory.
Our bodies are thermal, our body temperature is on average 36.6 degrees C. At such a low temperature, the activity of molecules / atoms is very low, so low that it is not enough to overcome the threshold of energetic reaction. Enzymes accelerate the course of the reaction and reduce the activation energy without increasing the body temperature. The increase in temperature increases the activity of enzymes (up to a certain threshold), however, remember that the body is mainly made of protein, and these are denatured at temperatures above 40 degrees C.
Therefore, enzymes have three basic characteristics
1) Increase the probability of collisions
The increase of collisions of particles or atoms occurs by compacting on the surface of the catalyst. In order for a chemical change to occur, molecules must be properly regulated. The rigid arrangement of functional groups that are to react with each other to the enzyme enables the rearrangement of electrons and bonds, which leads to the process being carried out.
2) Reduction of the energy barrier
Differently activation energy. Activation energy is the amount of energy that substrate molecules must have in order to create a product of a reaction during collisions. Otherwise, the molecules that are going to react do not come close to each other, they will not overcome the barrier of activation and not mature to the process.
From this it follows that raising the energy of activation is necessary. However, it is relatively smaller in catalytic reactions
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