Primary metabolites that make up the cell. Primary and secondary metabolism and metabolic products. taxols yew tree
A number of cell metabolites are of interest as target fermentation products. They are divided into primary and secondary.
Primary metabolites- These are low molecular weight compounds (molecular weight less than 1500 daltons) necessary for the growth of microorganisms. Some of them are the building blocks of macromolecules, others are involved in the synthesis of coenzymes. Among the most important metabolites for industry are amino acids, organic acids, nucleotides, vitamins, etc.
The biosynthesis of primary metabolites is carried out by various biological agents - microorganisms, plant and animal cells. In this case, not only natural organisms are used, but also specially obtained mutants. To ensure high concentrations of the product at the stage of fermentation, it is necessary to create producers that resist the regulatory mechanisms genetically inherent in their natural form. For example, it is necessary to eliminate the accumulation of an end product that represses or inhibits an important enzyme in order to obtain the target substance.
Production of amino acids.
Auxotrophs (microorganisms that require growth factors to reproduce) produce many amino acids and nucleotides during fermentations. Common objects for selection of amino acid producers are microorganisms belonging to the genera Brevibacterium, Corynebacterium, Micrococcus, Arthrobacter.
Of the 20 amino acids that make up proteins, eight cannot be synthesized in the human body (essential). These amino acids must be supplied to the human body with food. Among them, methionine and lysine are of particular importance. Methionine is produced by chemical synthesis, and more than 80% of lysine is produced by biosynthesis. The microbiological synthesis of amino acids is promising, since as a result of this process, biologically active isomers (L-amino acids) are obtained, and during chemical synthesis, both isomers are obtained in equal amounts. Since they are difficult to separate, half of the production is biologically useless.
Amino acids are used as food additives, seasonings, flavor enhancers, as well as raw materials in the chemical, perfumery and pharmaceutical industries.
The development of a technological scheme for obtaining a single amino acid is based on knowledge of the ways and mechanisms of regulation of the biosynthesis of a particular amino acid. The necessary imbalance of metabolism, which ensures the oversynthesis of the target product, is achieved by strictly controlled changes in the composition and environmental conditions. For the cultivation of strains of microorganisms in the production of amino acids, carbohydrates are the most available as carbon sources - glucose, sucrose, fructose, maltose. To reduce the cost of the nutrient medium, secondary raw materials are used: beet molasses, milk whey, starch hydrolysates. The technology of this process is being improved towards the development of cheap synthetic nutrient media based on acetic acid, methanol, ethanol, n-paraffins.
Production of organic acids.
Currently, a number of organic acids are synthesized by biotechnological methods on an industrial scale. Of these, citric, gluconic, ketogluconic and itaconic acids are obtained only by a microbiological method; milk, salicylic and acetic - both by chemical and microbiological methods; malic - chemically and enzymatically.
Acetic acid is the most important among all organic acids. It is used in the manufacture of many chemicals, including rubber, plastics, fibers, insecticides, and pharmaceuticals. The microbiological method for producing acetic acid consists in the oxidation of ethanol to acetic acid with the participation of bacteria strains Gluconobacter And Acetobacter:
Citric acid is widely used in the food, pharmaceutical and cosmetic industries, used to clean metals. The largest producer of citric acid is the USA. The production of citric acid is the oldest industrial microbiological process (1893). For its production use the culture of the fungus Aspergillus niger, A. wentii. Nutrient media for the cultivation of citric acid producers contain cheap carbohydrate raw materials as a carbon source: molasses, starch, glucose syrup.
Lactic acid is the first of the organic acids, which began to be produced by fermentation. It is used as an oxidizing agent in the food industry, as a mordant in the textile industry, and also in the production of plastics. Microbiologically, lactic acid is obtained from the fermentation of glucose Lactobacillus delbrueckii.
A. DEFINITION
From the point of view of biogenesis, antibiotics are considered as secondary metabolites. Secondary metabolites are low molecular weight natural products that are 1) synthesized only by certain types of microorganisms; 2) do not perform any obvious functions during cell growth and are often formed after the cessation of culture growth; cells that synthesize these substances easily lose their ability to synthesize as a result of mutations; 3) are often formed as complexes of similar products.
Primary metabolites are the normal products of cell metabolism, such as amino acids, nucleotides, coenzymes, etc., necessary for cell growth.
B. RELATIONSHIP BETWEEN THE PRIMARY
AND SECONDARY METABOLISM
The study of antibiotic biosynthesis consists in establishing the sequence of enzymatic reactions during which one or more primary metabolites (or intermediate products of their biosynthesis) are converted into an antibiotic. It must be remembered that the formation of secondary metabolites, especially in large quantities, is accompanied by significant changes in the primary metabolism of the cell, since in this case the cell must synthesize the starting material, supply energy, for example in the form of ATP, and reduced coenzymes. It is not surprising, therefore, that when strains synthesizing antibiotics are compared with strains that are not capable of synthesizing them, significant differences are found in the concentrations of enzymes that are not directly involved in the synthesis of a given antibiotic.
B. MAIN BIOSYNTHETIC PATHWAYS
Enzymatic reactions in the biosynthesis of antibiotics do not differ in principle from reactions in which primary metabolites are formed. They can be considered as a variation
reactions of biosynthesis of primary metabolites, of course, with some exceptions (for example, there are antibiotics containing a nitro group - a functional group that never occurs in primary metabolites and which is formed during the specific oxidation of amines).
Mechanisms for antibiotic biosynthesis can be divided into three main categories.
1. Antibiotics derived from a single primary metabolite. The path of their biosynthesis consists of a sequence of reactions that modify the initial product in the same way as in the synthesis of amino acids or nucleotides.
2. Antibiotics derived from two or three different primary metabolites that are modified and condensed to form a complex molecule. Similar cases are observed in the primary metabolism during the synthesis of certain coenzymes, such as folic acid or coenzyme A.
3. Antibiotics originating from polymerization products of several similar metabolites with the formation of a basic structure that can be further modified during other enzymatic reactions.
As a result of polymerization, four types of antibiotics are formed: 1) polypeptide antibiotics formed by condensation of amino acids; 2) antibiotics formed from acetate-propionate units in polymerization reactions similar to fatty acid biosynthesis; 3) terpenoid antibiotics derived from acetate units in the synthesis of isoprenoid compounds; 4) aminoglycoside antibiotics formed in condensation reactions similar to the reactions of polysaccharide biosynthesis.
These processes are similar to polymerization processes that provide the formation of some components of the membrane and cell wall.
It must be emphasized that the basic structure obtained by polymerization is usually further modified; it can even be joined by molecules produced by other biosynthetic pathways. Glycoside antibiotics are especially common - condensation products of one or more sugars with a molecule synthesized in path 2.
D. SYNTHESIS OF FAMILYS OF ANTIBIOTICS
Often strains of microorganisms synthesize several chemically and biologically close antibiotics that make up a "family" (antibiotic complex). The formation of "families" is characteristic not only for biosynthesis
Antibiotics, but is a common property of secondary metabolism associated with a rather large "size of intermediate products. The biosynthesis of complexes of related compounds is carried out in the course of the following metabolic pathways.
1. Biosynthesis of a "key" metabolite in one of the pathways described in the previous section.
Rifamycin U
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oxid.
Rice. 6.1. An example of a metabolic tree: the biosynthesis of rifamycin (see text for explanation; structural formulas of the corresponding compounds are shown in Figures 6.17 and 6.23).
2. Modification of a key metabolite using fairly common reactions, for example, by oxidizing a methyl group to an alcohol and then to a carboxyl group, reduction of double bonds, dehydrogenation, methylation, esterification, etc.
3. The same metabolite can be the substrate of two or more of these reactions, leading to the formation of two or more different products, which in turn can undergo various transformations with the participation of enzymes, giving rise to a "metabolic tree".
4. The same metabolite can be formed in two (or more) different ways, in which only
the order of enzymatic reactions, giving rise to the "metabolic network".
The rather peculiar concepts of the metabolic tree and metabolic network can be explained by the following examples: the biogenesis of the rifamycin family (tree) and erythromycin family (network). The first metabolite in the biogenesis of the rifamycin family is protorifamycin I (Fig. 6.1), which can be considered as a key metabolite. In sequence
reactions, the order of which is unknown, protorifamycin I is converted to rifamycin W and rifamycin S, completing part of the synthesis using a single pathway ("trunk" of the tree). Rifamycin S is the starting point for branching of several alternative pathways: condensation with a two-carbon fragment gives rise to rifamycin O and raphimycins L and B. The latter, as a result of the oxidation of the anza chain, turns into rifamycin Y. Cleavage of the one-carbon fragment during the oxidation of rifamycin S leads to the formation of rifamycin G , and as a result of unknown reactions, rifamycin S is converted into the so-called rifamycin complex (rifamycins A, C, D and E). Oxidation of the methyl group at C-30 gives rise to rifamycin R.
The key metabolite of the erythromycin family is erythronolide B (Er.B), which is converted to erythromycinA (the most complex metabolite) through the following four reactions (Fig. 6.2): 1) glycosylation at position 3 n
those of condensation with mycarosis (Mic.) (reaction I); 2) transformation of mycarose into cladinose (clad.) as a result of methylation (reaction II); 3) conversion of erythronolide B to erythronolide A (Er.A) as a result of hydroxylation at position 12 (reaction III); 4) condensation with deosamine (Des.) in position 5 (reaction IV).
Since the order of these four reactions can vary, different metabolic pathways are possible, and taken together they form the metabolic network shown in Fig. 6.2. It should be noted that there are also paths that are a combination of a tree and a network.
NATIONAL PHARMACEUTICAL UNIVERSITY SPECIALTY "BIOTECHNOLOGY"
DISCIPLINE "GENERAL MICROBIOLOGY AND VIROLOGY" DEPARTMENT OF BIOTECHNOLOGY
BIOSYNTHETIC PROCESSES IN MICROORGANISMS.
BIOSYNTHESIS OF PRIMARY METABOLITES: AMINO ACIDS, NUCLEOTIDES, CARBOHYDRATES, FATTY ACIDS.
BIOSYNTHETIC PROCESSES IN MICROORGANISMS
BIOSYNTHESIS OF AMINO ACIDS
INDUSTRIAL OBTAINING OF AMINO ACIDS
BIOSYNTHESIS OF NUCLEOTIDES
INDUSTRIAL OBTAINING OF NUCLEOTIDES
BIOSYNTHESIS OF FATTY ACIDS, CARBOHYDRATES, SUGAR
BIOSYNTHETIC PROCESSES IN MICROORGANISMS
METABOLISM
GLUCOSE*
FIGURE 1 - GENERAL SCHEME OF WAYS OF CELL MATERIAL BIOSYNTHESIS
FROM GLUCOSE
AMPHIBOLISM CATABOLISM
PENTOSOPHOSPHATES |
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PHOSPHOENOLPYRUVATE |
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MONOMERS |
POLYMERS |
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Amino acids |
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ACETYL COA |
vitamins |
Polysaccharides |
Sugarphosphates |
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Fatty acid |
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OXALOACETATE |
Nucleotides |
Nucleic |
2-OXOGLUTARATE
BIOSYNTHETIC PROCESSES
At MICROORGANISMS
IN the process of growth of microorganisms on glucose under aerobic conditions is about 50%
glucose is oxidized to CO2 for energy. The remaining 50% of glucose is converted into cellular material. It is for this transformation that most of the ATP formed during the oxidation of the substrate is spent.
METABOLITES
MICROORGANISMS
Metabolites are formed at different stages of microbial growth.
In the logarithmic growth phase, primary metabolites (proteins, amino acids, etc.) are formed.
In the lag phase and in the stationary phase, secondary metabolites are formed, which are biologically active compounds. These include various antibiotics, enzyme inhibitors, etc.
METABOLITES
MICROORGANISMS
Primary metabolites- these are low molecular weight compounds (molecular weight less than 1500 daltons) necessary for the growth of microbes; some of them are the building blocks of macromolecules, others are involved in the synthesis of coenzymes. Amino acids, organic acids, purine and primidine nucleotides, vitamins, etc., can be distinguished among the most important metabolites for industry.
Secondary metabolites- These are low molecular weight compounds formed at the later stages of culture development, which are not required for the growth of microorganisms. By chemical structure, secondary metabolites belong to different groups of compounds. These include antibiotics, alkaloids, plant growth hormones, toxins, and pigments.
Microorganisms - producers of primary and secondary metabolites are used in industry. The initial strains for industrial processes are natural organisms and cultures with dysregulation of the synthesis of these metabolites, since ordinary microbial cells do not produce7 excess primary metabolites.
Questions:
1. Metabolism. Primary and secondary metabolism.
2. Features of cellular metabolism.
3. Cell as an open thermodynamic system. Types of work in the cell. macroergic compounds.
4. Enzymes: structure (prostatic group, coenzymes) and functions. Enzyme classification
5. Secondary metabolites, classification, role in plant life, human use. Formation of pigments, toxins, aromatic substances by microorganisms (fungi, bacteria).
1. Metabolism (metabolism) - the totality of all chemical reactions that take place in the cell.
Metabolites - products of metabolism.
On the formation of hormones in cells (ethylene, inhibit the synthesis of IAA);
Inhibit rhizogenesis and cell elongation;
They are phytotoxins (have an antimicrobial effect);
With their help, one plant can act on another,
Tannins increase the resistance of trees to fungal infections.
Are used in medicine for sterilization, drugs (salicylic acid), in industry as dyes.
5.2. alkaloids - heterocyclic compounds containing one or more nitrogen atoms in the molecule. About 10,000 alkaloids are known. They are found in 20% of plants, most common among angiosperms (flowering) plants. In bryophytes and ferns, alkaloids are rare.
Alkaloids are synthesized from amino acids: ornithine, tyrosine, lysine, tryptophan, phenylalanine, histidine, atranilic acid.
They accumulate in actively growing tissues, in the cells of the epidermis and hypodermis, in the lining of the vascular bundles, in the lactifers. They can accumulate not in those cells where they are formed, but in others. For example, nicotine is formed in the roots and accumulates in the leaves. Usually their concentration is tenths or hundredths of a percent, but cinchona contains 15 - 20% alkaloids. Different plants may contain different alkaloids. Alkaloids are found in leaves, bark, roots, wood.
Functions alkaloids:
regulate plant growth (IAC), protect plants from being eaten by animals.
Are used alkaloids
as drugs: codeine (for cough), morphine (painkiller), caffeine (for nervous and cardiovascular diseases), quinine (for malaria). Atropine, pilocarpine, strychnine, ephedrine are poisonous, but in small doses they can be used as medicines .;
nicotine, anabazine are used to fight insects.
5.3. Isoprenoids (terpenoids) - compounds composed of several isoprene units (С5Н8 - isoprene) and having the general formula (С5Н8) n. Due to additional groups (radicals), isoprenoids can have a number of carbon atoms in the molecule and not a multiple of 5. Terpenes include not only hydrocarbons, but also compounds with alcohol, aldehyde, keto, lactone and acid groups.
Polyterpenes - rubber, gutta.
Terpenoids are gibberellic acid (gibberellins), abscisic acid, cytokinins. They don't dissolve in water. They are found in chloroplasts, in membranes.
Carotenoids are colored from yellow to red-violet, are formed from lycopene, and are soluble in fats.
Isoprenes are included
in the composition of the oil of needles, cones, flowers, fruits, wood;
resins, latex, essential oils.
Functions:
Protect plants from bacteria, insects and animals; some of them are involved in closing wounds and protecting against insects.
These include hormones (cytokinins, gibberellins, abscisic acid, brassinosteroids);
Carotenoids are involved in the light phase of photosynthesis, entering the SSC, and protect chlorophyll from photooxidation;
Sterols are part of the membranes, affect their permeability.
use as drugs (camphor, menthol, cardiac glycosides), vitamin A. They are the main components of essential oils, so they are used in perfumery, contained in repellents. Included in rubber. Geraniol alcohol is part of rose oil, bay leaf oil, orange flower oil, jasmine oil, eucalyptus oil).
5.4. Synthesis of secondary metabolites
characterized by some features:
1) their precursors are a small number of primary metabolites. For example, for the synthesis of alkaloids, 8 (?) amino acids are needed, for the synthesis of phenols - phenylalanine or tyrosine, for the synthesis of isoprenoids - mevalonic acid;
2) many secondary metabolites are synthesized in different ways;
3) special enzymes are involved in the synthesis.
Secondary metabolites are synthesized in the cytosol, endoplasmic reticulum, chloroplasts.
5.5. Localization of secondary metabolites
They accumulate in vacuoles (alkaloids, phenols, betalains, cyanogenic glycosides, glucosinolates), in the periplasmic space (phenols). Isoprenoids exit the cell after synthesis.
Secondary metabolites are rarely evenly distributed in tissues. Often they accumulate in idioblasts, lactic cells, special channels and passages.
Idioblasts (from Greek. Idios peculiar) - single cells belonging to excretory tissues and differing from neighboring cells in shape, structure. They are found in the epidermis of stems or leaves (only in the epidermis?).
The sites of synthesis and localization are often separated. For example, nicotine is synthesized in roots and stored in leaves.
Secondary metabolites are released into the external environment with the help of excretory tissues (glandular cells, glandular hairs - trichomes).
For alkaloids, isolation is uncharacteristic.
The synthesis and accumulation of secondary metabolites in tissues depends mainly on the plant species, sometimes on the stage of ontogenesis or age, and on external conditions. Distribution in tissues depends on the type of plant.
5.6. Functions of secondary metabolites
During the discovery of secondary metabolites, there were different opinions about their significance in plant life. They were considered unnecessary, waste, (their synthesis) a dead end of metabolism, detoxification products of poisonous primary metabolites, such as free amino acids.
Many are already known functions these compounds, for example, storage, protective. Alkaloids are a supply of nitrogen for cells, phenolic compounds can be a respiratory substrate. Secondary metabolites protect plants from biopathogens. Essential oils, which are a mixture of secondary metabolites, have antimicrobial and antifungal properties. Some secondary metabolites, decomposing during hydrolysis, form poison - hydrocyanic acid, coumarin. Secondary metabolites are phytoalexins, substances formed in response to infection and involved in hypersensitivity reactions.
Anthocyanins, carotenoids, betalains, which provide the color of flowers and fruits, promote plant reproduction and seed dispersal.
Secondary metabolites stop seed germination of competing species.
Literature:
1. Mercer E. Introduction to plant biochemistry. T. 2. - M. "Mir", 1986.
2. (ed.). Physiology of plants. - M. "Academy", 2005. S. 588 - 619.
3. Harborn J. An Introduction to Environmental Biochemistry. - M. "Mir", 1985.
4. L. Biochemistry of plants. - M. "Higher School", 1986. S. 312 - 358.
5. , -AND. Physiology of woody plants. - M. "Forest Industry", 1974. 421 p.
6. L. Biochemistry of plants. - M. VS. 1986. 502 p.
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By metabolism, or metabolism, is meant a set of chemical reactions in the body that provide it with substances to build the body and energy to maintain life.
primary metabolism
Part of the reactions turns out to be similar for all living organisms (formation and cleavage of nucleic acids, proteins and peptides, as well as most carbohydrates, some carboxylic acids, etc.) and is called primary metabolism, or primary metabolism.
secondary metabolism
In addition to primary exchange reactions, there is a significant number of metabolic pathways leading to the formation of compounds that are characteristic only of certain, sometimes very few, groups of organisms. These reactions, according to I. Chapek (1921) and K. Pah (1940), are combined by the term secondary metabolism, or secondary exchange, and the products are called products of secondary metabolism, or secondary connections(sometimes, which is not entirely true, secondary metabolites). However, it should be emphasized that the differences between primary and secondary metabolism are not very sharp.
Secondary connections are formed mainly in vegetatively inactive groups of living organisms - plants and fungi, as well as many prokaryotes. In animals, the products of secondary metabolism are relatively rare and often come from outside along with plant foods. The role of products of secondary metabolism and the reasons for their appearance in a particular group are different. In the most general form, they are assigned an adaptive role and, in a broad sense, protective properties.
The rapid development of the chemistry of natural compounds over the past four decades, associated with the creation of high-resolution analytical tools, has led to the fact that the world of "secondary compounds" has expanded significantly. For example, the number of alkaloids known today is approaching 5,000 (according to some sources - 10,000), phenolic compounds - to 10,000, and these numbers are growing not only every year, but also every month.
Any plant raw material always contains a complex set of primary and secondary compounds, which, as mentioned above, determine the multiple nature of the action of medicinal plants. However, the role of both in modern phytotherapy is still different. Relatively few plant objects are known, the use of which in medicine is determined primarily by the presence of primary compounds in them. However, in the future, their role in medicine and their use as sources for obtaining new immunomodulating agents cannot be ruled out.
Secondary exchange products are applied in modern medicine is much more common and wider. This is due to a tangible and often very bright pharmacological effect. Formed on the basis of primary compounds, they can accumulate either in pure form or undergo glycosylation during exchange reactions, i.e. are attached to a sugar molecule. As a result of glycosylation, molecules are formed - heterosides, which differ from non-glycosylated secondary compounds, as a rule, in better solubility, which facilitates their participation in metabolic reactions and is of great biological importance in this sense. Glycosylated forms of any secondary compounds are called glycosides.