Pigmentary exchange - the whole process of education, transformation and decay in living organisms painted organic substances complicated chemical structure - pigments. The most important pigments - porphyrins, chromoproteids, melanin, carotenoids, flavones (see) and other Such chromoproteids as hemoglobin (see), myoglobin, catalase, cytochromes (see Enzymes), as prosthetic (i.e. non-protein) groups contain zhelezohromovye complex (gem). The formation of hemoglobin is in hematopoietic cells of the bone marrow; myoglobin is formed, apparently, within the muscle fibres, and cytochromes and catalase directly in the containing tissues. In the biosynthesis porphyrinogenesis pigments first synthesis of protoporphyrin (of succinic acid and glycine), which then turns on atom of iron, and the result is a gem. After accession to the corresponding protein completes the synthesis of different chromoprotein. In the biological breakdown porphyrin protein pigments are released iron and protein, and protoporphyrin turns into bile pigment (see). Bilirubin (see) in the intestine becomes the urobilin (see) and stercobilin (see), which are excreted from the body in the composition of feces. Biliverdin is excreted in unchanged form. Part of bile pigments excreted in the urine.
Among other pigments are important pigments in the skin and hair melanin is formed from phenylalanine and tyrosine, and carotenoids. Out of beta carotene in the bowel wall formed vitamin a, which in the retina of the eye turns into Reinin, and then connecting with protein, the protein (see) is a substance that is involved in photochemical reactions of the retina.
In the chain of reactions of synthesis and transformations of pigments can occur pathological violations, leading to serious diseases. So, by blocking certain stages of the biosynthesis of phthalocyanine pigments comes porphyria, accompanied by anemia (a sharp reduction in the formation of hemoglobin) and porphyrinuria (allocation of urine and intermediate products pigmentary exchange). In all cases of hemolysis increases the breakdown of hemoglobin. Under the influence of some poisons (e.g. cyanide, carbon monoxide can cause oxidation of hemoglobin with the formation of methemoglobin. The consequence of deep violation of the synthesis of hemoglobin is the formation of various forms of abnormal hemoglobins (emerging in a number of hereditary diseases).
Pigmentary exchange - the whole process of education, transformation and dissolution of pigments (see) in living organisms.
The synthesis of hemoglobin and related pigments. The formation of hemoglobin is in the process of maturation of hematopoietic stem cells from bone marrow, while myoglobin is formed, apparently, within the muscle fibres, and cytochromes and cytochrome oxidase - directly in the containing tissues, and the concentration of cytochrome in various tissues of the same animal proportional to the intensity of breathing in this tissue and to some extent depends on the power of the body.
In the process of biosynthesis of hemoglobin and myoglobin, the formation of tetrapyrrole ring protoporphyrin (see Porphyrins), the inclusion of iron and a subsequent connection formed zhelezovanadievoj complex (heme) with protein - Globino. In the animal organism ring of protoporphyrin IX (type III) is derived from acetic acid and glycine. Acetic acid, including in the tricarboxylic acid cycle (see biological Oxidation), turns into amber acid, which with the participation of coenzyme a (see Enzymes) is condensed with alpha-carbon atom of glycine and turns into α-amino-beta-ketodienes acid. This acid, losing carboxyl group enters α aminolevulinova acid; two molecules of this acid by condensation to form a circular connection - porphobilinogen. Porphobilinogen is a direct predecessor perlovich rings porphyrin molecule.
From molecules of porphobilinogen synthesized then tetrapyrrole ring of porphyrins. General predecessor of porphyrins is a substance, called porphyrinogenic. Porfirinova and other intermediate in the biosynthesis of hemoglobin quickly appear and
quickly disappear, becoming protoporphyrin III forms of hem - enzymes number chromoproteids. At transformation of porphyrinogenic in porphyrins formed mainly protoporphyrin III and only in a small number of porphyrin I, which is not used in the body and extracted from it in the form of coproporphyrin I. the Number of protoporphyrin III generated per day in the body, is 300 mg daily allocation of this substance in the form of coproporphyrin III is only 0.1 mg Thus, almost all synthesized protoporphyrin III is the construction of hemoglobin, myoglobin and other chromoproteids.
Synthesized in the animal organism protoporphyrin III, adding the iron turns into a gem. This zhelezohromovye complex is not substance specific pigment, because it is part of a number of complex proteins, such as hemoglobin, myoglobin and other Heme in the future is connected with specific proteins, turning into a molecule of hemoglobin, myoglobin, cytochrome C, etc. During the synthesis of cytochrome C is a restoration of the vinyl groups of protoporphyrin in ethyl group. Thus, the formation of various chromoproteids depends on what kind of specific proteins, is that the cells in which the synthesis of this pigment. In humans and higher vertebrates are synthesized only zhelezopatna. In the process of biosynthesis of hemoglobin and other kindred pigments used iron as released by the decay of red blood cells, and from food. The inclusion of iron in red blood cells occurs only at the moment of their formation. The lack of iron in the organism, leads to decrease of hemoglobin synthesis, but does not affect the formation of cytochrome C, myoglobin and catalase. For the synthesis of a protein part chromoproteids tissue and blood are used amino acids, released in the process of destruction of relevant Globino.
The rate of biosynthesis of various chromoproteids unequal. Education myoglobin and cytochrome C is happening more slowly than the synthesis of hemoglobin.
The breakdown of hemoglobin and close to him pigments. In the biological breakdown of hemoglobin is the release of iron and globin used for the synthesis of new molecules of pigment in the blood. Protoporphyrin same turns into bile pigment (see). All of these reactions take place in coppersky liver cells and phagocytic cells of the reticuloendothelial system, but their order is still insufficiently understood. In the beginning of the destruction of hemoglobin and myoglobin are formed green pigments - perdagangan. At transformation of pigments muscles and blood in perdagangan is ring-opening of protoporphyrin (preserving its links with iron and Globino) as a result of the break α methine bridge with the simultaneous oxidation of the first and second rings pyrrol. Perdagangan, losing iron and globin, turns into bile pigments: initially formed biliverdin, which then under the influence of cell digitas restored and transformed into bilirubin. The main source of bile pigments is a prosthetic group of hemoglobin, and then and myoglobin. In bile pigments, apparently, become a prosthetic group of cytochrome C and catalase; however, as a result of their decay produces only 5% of the total number of bile pigments. Assume that a certain amount of bile pigments can occur directly from protoporphyrin III, and possibly of heme to use these substances in the synthesis of hemoglobin. Part collapsing pigments muscles and blood can turn and in coproporphyrin III.
Bile pigment formed in the cells of the reticuloendothelial system, enter the bloodstream in the form of bilirubin. In blood bilirubin is connected with serum albumin and turns into bilirubin-protein complex, which is captured by the liver. From the liver biliverdin and free bilirubin is excreted in the gallbladder and from there into the intestine.
In the intestines bilirubin under the influence of intestinal bacteria restored in urobilinogen and stercobilinogen, colorless form (leucosolenia) pigments urine and feces. Of these LEUCO compounds are formed in the oxidation of the urobilin and stercobilin.
The bulk of urobilinogen and stercobilinogen out from the body through the intestine, but some is absorbed, falls into the liver, where it turns into bilirubin, partially enters the blood and excreted by the kidneys with urine in the form of urobilin and stercobilin (so-called General urobilin urine, the amount of which usually varies in the range of 0.2 to 2 mg per day and normally do not exceed 4 mg). In contrast to bilirubin, biliverdin in the intestine is not exposed to influence of microflora and excreted from the body in an unmodified form. Some part of bilirubin can oxidize and become biliverdin.
Along with the formation of bile pigments (tetrapyrrol with open circuit), which are the main end product of hemoglobin and other chromoproteids in the liver may occur and deeper collapse of heme and bilirubin education diperoleh compounds propanediamine and Belarussia. Belfastin in the intestine undergoes recovery, and then connecting with protein, turns into a brown pigment - mobilen. Propanediamine and mobilin detected in the urine and fecal matter.
Currency of some other pigments. Dark brown and black
lack of melanin production (see) - are formed in the body of phenylalanine and tyrosine under the influence of tyrosinase, and initially phenylalanine is oxidized in the tyrosine. Although only a small amount of free tyrosine cells become melanin, this process plays a major role in the formation of the pigment of the skin and hair. Tyrosine are oxidized, enters 3,4-di-oxigenului that under the influence of a special enzyme of dioxyphenilalanin oxidase (Dov-oxidase) breaks down, and resulting from the decay products then there melanin. The formation of melanin can also occur from substances such as red-yellow pigment xendomain and 3-oxichinolinr - product of the metabolism of tryptophan. The carotenoid pigments nature not essential for the formation of melanin.
From a variety of transformations in living organisms carotenoids (see) deserves special attention transition carotene into vitamin A. it is Proved that vitamin a (see) is formed mainly of (5-carotene in the bowel wall, but not in the liver as it was supposed earlier. However, there is still a sufficient reason to completely deny the role of the liver in this important process. In the intestinal wall under the influence, apparently, enzyme keratinase there is a decomposition of molecules of beta-carotene, entering the body with meal. This first beta-carotene is oxidative decomposition with the formation of aldehyde vitamin - kretinina, which then quickly turns into vitamin A. Formed vitamin a comes to the blood in large quantities and stored in the liver and partially delayed a number of other organs and tissues.
In the retina of the eye vitamin a can reversible turning into Reinin, in connection with which the protein opcina formed rhodopsin (see), or visual purple, which is the photochemical sensitizer.
Pathology pigmentary exchange. In various diseases in humans may result in different disorders in the exchange of hemoglobin. A clear manifestation of disorders in biosynthetic reactions are porfirii, at which as a result of the failure of the relevant enzyme systems are blocked certain stages of protoporphyrins III and heme. A visual representation of the place of metabolic damage during synthetic reactions in this congenital pathology of porphyrin metabolism gives scheme (see below).
The scheme metabolic damage in the chain of reactions leading to the formation of heme when porfirian.
In acute porfirii violated the transformation of porphobilinogen in porfirinova. Consequently, at the beginning of the attack with urine excreted red pigment portabilling and his colorless form - porphobilinogen that when standing spontaneously turns into portabilling. Also, are removed from the body of a small number Uro - and coproporphyrin I and III types in the form of zinc compounds. Congenital porphyria is characterized by the increased production of Uro - and coproporphyrin I type. Bones and teeth in patients become red or brown deposits in them porphyrins. In the urine free Uro - and coproporphyrin I and traces of protoporphyrin III, and in fecal matter - of coproporphyrin I. In the case of cutaneous forms of porphyria in the period of remission from the body is excreted by the kidneys and through the intestines about 20% of all normally formed in it protoporphyrin. During the attack porphyrins are allocated only with urine in the form of Uro - and coproporphyrin I and III types.
Porphyrinuria observed and some other diseases as a consequence of the increase in the body of the number of free porphyrins, which are by-products in the biosynthesis of heme. So, in aplastic anemia and polio dominates the selection of coproporphyrin III, while in cases of pernicious anemia, leukemia, hemophilia, infectious hepatitis and other diseases mainly stands out coproporphyrin I.
Pathological changes in the exchange of hemoglobin are with anemia (see). For example, iron deficiency anemia characterized by a sharp reduction in the formation of hemoglobin due to depletion depot iron in the body, iron deficiency in bone marrow, etc., without pernicious anemia hemoglobin formation slowed, part of immature red blood cells are destroyed in the bone marrow, resulting in increased levels of bile pigments and bilirubinuria. In the urine detected urobilin (stercobilin), and in Cala increased content stercobilin (urobilin).
Strengthening the breakdown of hemoglobin is observed in all cases of hemolysis (see), which released a significant amount of hemoglobin, there hemoglobinemia, hemoglobinuria (see), increases the formation of bile pigments and their transformation into pigments urine and feces.
Under the influence of certain toxic substances in the blood may occur oxidation of hemoglobin with the formation of brown pigment - methemoglobin. In cases of severe poisoning methemoglobin excreted in the urine. It is possible deposition of methemoglobin and its breakdown product - gelatina - in the renal tubules, resulting in the violation of the filtration ability of kidneys and development of uremia (see).
Metabolic myoglobin occurs for a number of diseases, accompanied by the release of myoglobin from the muscles and release it from urine. These little known disease under the General title of mioglobinurii. They are found in animals (paralytic, myoglobinuria horses, white-muscle disease), rare in humans. When myoglobinuria observed abnormal mobilization of myoglobin, loss of red muscle regular color, atrophic or degenerative changes in the muscle tissue. The myoglobinuria a person occurs as a result of traumatic injuries of the muscles after a long marches, great physical strain, some forms of muscular dystrophy, etc.,
Deep disruption in the synthesis of hemoglobin, bearing not only quantitative, but also qualitative, are observed at sickle cell anemia (see).
In patients suffering from this disease, synthesized a special kind of hemoglobin hemoglobin S, amino acid composition of which differs from normal hemoglobin in respect of one amino acid in hemoglobin S instead of molecules glutamic acid, standing in the polypeptide chain, is the amino acid valine). This is a small difference in the structure dramatically affects hemoglobin S, which is poorly soluble in water and falls inside of red blood cells in the form of crystals, making red blood cells take sickle shape.
In the process of the physiological collapse of tyrosine it deamination and further oxidation with the formation of an intermediate product of the collapse homogentisic acid. If alkaptonuria disturbed oxidation homogentisic acid; it is excreted by the kidneys and alkaline urine turns into a brown-black melaninogenica pigment, the structure of which is not yet established.
Cm. also, Nitrogen metabolism, Blood, Metabolism and anergy.
