Aldehyde dehydrogenases ( EC 1.2.1.3 ) are a group of enzymes that catalyse the oxidation of aldehydes . They convert aldehydes (R–C(=O) –H ) to carboxylic acids (R–C(=O) –O–H ). The oxygen comes from a water molecule. To date, nineteen ALDH genes have been identified within the human genome. These genes participate in a wide variety of biological processes including the detoxification of exogenously and endogenously generated aldehydes.
51-495: Azotobacter agilis Azotobacter armeniacus Azotobacter beijerinckii Azotobacter chroococcum Azotobacter nigricans Azotobacter salinestris Azotobacter tropicalis Azotobacter vinelandii Azotobacter is a genus of usually motile , oval or spherical bacteria that form thick-walled cysts (and also has hard crust) and may produce large quantities of capsular slime . They are aerobic, free-living soil microbes that play an important role in
102-732: A biofertilizer , fungicide, and nutrient indicator, and in bioremediation . A. chroococcum is a microaerophilic plant growth-promoting rhizobacterium (PGRP), which is bacillus in shape and is Gram negative. As a mesophile, this bacterium grows best in moderate-temperature soils and requires a neutral pH environment. It is able to fix nitrogen under aerobic conditions. The soil cannot be poor in phosphorus or else nitrogen fixing can be hindered. In addition to phosphorus, these bacteria needed potassium, "sulphur, magnesium, and calcium" to grow. To fix nitrogen A. chroococcum produces three enzymes ( catalase , peroxidase , and superoxide dismutase ) to "neutralise" reactive oxygen species. It also forms
153-419: A simple division . During the germination, the cysts sustain damage and release a large vegetative cell. Microscopically, the first manifestation of spore germination is the gradual decrease in light refractive by cysts, which is detected with phase contrast microscopy . Germination of cysts takes about 4–6 h. During germination, the central body grows and captures the granules of volutin, which were located in
204-464: A cysteine in the active site makes a nucleophilic attack on the carbonyl carbon of the aldehyde. The hydrogen is kicked off as a hydride and attacks NAD(P) to make NAD(P)H . The enzyme's active site then goes through an isomorphic change whereby the NAD(P)H is moved, creating room for a water molecule to access the substrate. The water is primed by a glutamate in the active site, and the water makes
255-521: A dark-brown water-soluble pigment melanin . This process occurs at high levels of metabolism during the fixation of nitrogen, and is thought to protect the nitrogenase system from oxygen. Other Azotobacter species produce pigments from yellow-green to purple colors, including a green pigment which fluoresces with a yellow-green light and a pigment with blue-white fluorescence. The nucleotide sequence of chromosomes of Azotobacter vinelandii , strain AvOP,
306-581: A diameter of 5–10 mm, which may form films in liquid nutrient media. The colonies can be dark-brown, green, or other colors, or may be colorless, depending on the species. The growth is favored at a temperature of 20–30°C. Bacteria of the genus Azotobacter are also known to form intracellular inclusions of polyhydroxyalkanoates under certain environmental conditions (e.g. lack of elements such as phosphorus, nitrogen, or oxygen combined with an excessive supply of carbon sources). Azotobacter produces pigments . For example, Azotobacter chroococcum forms
357-508: A nucleophilic attack on the carbonyl carbon, kicking off the sulfur as a leaving group . Researchers at the University of Tsukuba found that durian extract inhibited aldehyde dehydrogenase activity, lending credence to an Asian folklore warning against consuming durian with alcohol. ALDH2 plays a crucial role in maintaining low blood levels of acetaldehyde during alcohol oxidation. In this pathway ( ethanol to acetaldehyde to acetate ),
408-736: A potential mechanism through which environmental toxicants contribute to PD pathogenesis." Knockout mouse models further confirm the involvement of ALDH family in neurodegeneration. Mice null for ALDH1a1 and ALDH2 exhibit Parkinson's disease-like age-dependent deficits in motor performance and significant increase in biogenic aldehydes. The ALDH2-/- mice display age-related memory deficits in various tasks, as well as endothelial dysfunction, brain atrophy, and other Alzheimer's disease-associated pathologies, including marked increases in lipid peroxidation products, amyloid-beta , p-tau and activated caspases . These behavioral and biochemical Alzheimer's disease-like deficits were efficiently ameliorated when
459-503: A significant increase in crop production linked to the production of "auxins, cytokinins, and GA–like substances" by A. chroococcum . In addition to these biomolecules, this bacterium has been found to be able to produce "siderophores, ammonia, and ACC deaminase", as well as indoleacetic acid, which all are known to assist with the growth of crops. On top of helping with the growth of crops in general, A. chroococcum has also been shown to help crops grow in polluted soils. A. chroococcum
510-426: A similar reaction known as disulfiram-like reaction . Yokoyama et al. found that decreased enzyme activity of aldehyde dehydrogenase-2, caused by the mutated ALDH2 allele, contributes to a higher chance of esophageal and oropharyngolaryngeal cancers. The metabolized acetaldehyde in the blood, which is six times higher than in individuals without the mutation, has shown to be a carcinogen in lab animals. ALDH2*2
561-411: Is a mutant form of aldehyde dehydrogenase, termed ALDH2*2, wherein a lysine residue replaces a glutamate in the active site at position 487 of ALDH2. Homozygous individuals with the mutant allele have almost no ALDH2 activity, and those heterozygous for the mutation have reduced activity. Thus, the mutation is partially dominant. The ineffective homozygous allele works at a rate of about 8% of
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#1732854763998612-500: Is a potentially important, poor prognostic factor in breast cancer, associated with high histological grade, estrogen/progesteron receptor negativity and HER2 positivity. Some case-control studies claimed that carriage of ALDH2*2 allele was a risk of late-onset Alzheimer's disease independent of the apolipoprotein E gene (the odds for LOAD in carriers of ALDH2*2 allele almost twice that of non-carriers). Moreover, ALDH gene, protein expression and activity are substantially decreased in
663-415: Is able to survive and improve the growth of crops in soils polluted with heavy metals when seeds are inoculated with the bacterium prior to planting. A. chroococcum not only produced growth-positive biomolecules and increased the number and quality of maize kernels, but also reduced the production of "proline, antioxidant enzymes, and MDA" in the plants, all which indicate of the presence of heavy metals in
714-400: Is associated with increased odds of oropharyngolaryngeal, esophageal, gastric, colon, and lung cancer. However, they found no connection between increased levels of ALDH2*2 in the blood and an increased risk of liver cancer. High expression of the genes that encode ALDH1A1 and ALDH2 is associated with a poor prognosis in patients with acute myeloid leukemia. Demir et al. found that ALDH1
765-428: Is induced by chemical factors and is accompanied by metabolic shifts, changes in catabolism , respiration , and biosynthesis of macromolecules ; it is also affected by aldehyde dehydrogenase and the response regulator AlgR. The cysts of Azotobacter are spherical and consist of the so-called "central body" – a reduced copy of vegetative cells with several vacuoles – and the "two-layer shell". The inner part of
816-468: Is manifested by slow acetaldehyde removal, with low alcohol tolerance perhaps leading to a lower frequency of alcoholism. These symptoms are the same as those observed in people who drink while being treated by the drug disulfiram , which is why disulfiram is used to treat alcoholism. The patients show higher blood levels of acetaldehyde, and become violently ill upon consumption of even small amounts of alcohol. Several drugs (e.g., metronidazole ) cause
867-509: Is more active than the Mo-Fe nitrogenase at low temperatures. So it can fix nitrogen at temperatures as low as 5 °C, and its low-temperature activity is 10 times higher than that of Mo-Fe nitrogenase. An important role in maturation of Mo-Fe nitrogenase plays the so-called P-cluster. Synthesis of nitrogenase is controlled by the nif genes. Nitrogen fixation is regulated by the enhancer protein NifA and
918-526: Is not fixed, the source of nitrogen can alternatively be nitrates , ammonium ions, or amino acids . The optimal pH for the growth and nitrogen fixation is 7.0–7.5, but growth is sustained in the pH range from 4.8 to 8.5. Azotobacter can also grow mixotrophically , in a molecular nitrogen-free medium containing mannose ; this growth mode is hydrogen-dependent. Hydrogen is available in the soil, thus this growth mode may occur in nature. While growing, Azotobacter produces flat, slimy, paste-like colonies with
969-494: Is partially determined. This chromosome is a circular DNA molecule which contains 5,342,073 nucleotide pairs and 5,043 genes, of which 4,988 encode proteins. The fraction of guanine + cytosine pairs is 65 mole percent. The number of chromosomes in the cells and the DNA content increases upon aging, and in the stationary growth phase, cultures may contain more than 100 copies of a chromosome per cell. The original DNA content (one copy)
1020-470: Is restored when replanting the culture into a fresh medium. In addition to chromosomal DNA, Azotobacter can contain plasmids . Azotobacter species are ubiquitous in neutral and weakly basic soils , but not acidic soils. They are also found in the Arctic and Antarctic soils, despite the cold climate, short growing season, and relatively low pH values of these soils. In dry soils, Azotobacter can survive in
1071-501: The intima (the innermost layer). Then, the exine bursts and the vegetative cell is freed from the exine, which has a characteristic horseshoe shape. This process is accompanied by metabolic changes. Immediately after being supplied with a carbon source, the cysts begin to absorb oxygen and emit carbon dioxide ; the rate of this process gradually increases and saturates after four hours. The synthesis of proteins and RNA occurs in parallel, but it intensifies only after five hours after
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#17328547639981122-420: The nitrogen cycle in nature, binding atmospheric nitrogen , which is inaccessible to plants, and releasing it in the form of ammonium ions into the soil ( nitrogen fixation ). In addition to being a model organism for studying diazotrophs , it is used by humans for the production of biofertilizers , food additives , and some biopolymers . The first representative of the genus, Azotobacter chroococcum ,
1173-542: The substantia nigra of Parkinson's disease patients. These reports are in line with findings implementing toxic lipid oxidation-derived aldehydes in these diseases and in neurodegeneration in general. Fitzmaurice et al. explored aldehyde dehydrogenase inhibition as a pathogenic mechanism in Parkinson disease. "This ALDH model for PD etiology may help explain the selective vulnerability of dopaminergic neurons in PD and provide
1224-540: The "sensor" flavoprotein NifL which modulates the activation of gene transcription of nitrogen fixation by redox -dependent switching. This regulatory mechanism, relying on two proteins forming complexes with each other, is uncommon for other systems. Nitrogen fixation plays an important role in the nitrogen cycle. Azotobacter also synthesizes some biologically active substances, including some phytohormones such as auxins , thereby stimulating plant growth. They also facilitate
1275-401: The absence of a nitrogen source in the medium. Homocitrate ions play a certain role in the processes of nitrogen fixation by Azotobacter . Nitrogenase is the most important enzyme involved in nitrogen fixation. Azotobacter species have several types of nitrogenase. The basic one is molybdenum-iron nitrogenase. An alternative type contains vanadium ; it is independent of molybdenum ions and
1326-412: The addition of the carbon source. The synthesis of DNA and nitrogen fixation are initiated 5 hours after the addition of glucose to a nitrogen-free nutrient medium. Germination of cysts is accompanied by changes in the intima, visible with an electron microscope. The intima consists of carbohydrates , lipids , and proteins and has almost the same volume as the central body. During germination of cysts,
1377-752: The amount of nitrogen that has to be added to fields, which can reduce the amount of nitrogen runoff. This effect of less nitrogen being added in soil was seen in a study involving cotton plants. This Pseudomonadales article is a stub . You can help Misplaced Pages by expanding it . Aldehyde dehydrogenase Aldehyde dehydrogenase is a polymorphic enzyme responsible for the oxidation of aldehydes to carboxylic acids . There are three different classes of these enzymes in mammals: class 1 (low K m , cytosolic), class 2 (low K m , mitochondrial), and class 3 (high K m , such as those expressed in tumors, stomach, and cornea). In all three classes, constitutive and inducible forms exist. ALDH1 and ALDH2 are
1428-462: The atmosphere without symbiotic relations with plants, although some Azotobacter species are associated with plants. Nitrogen fixation is inhibited in the presence of available nitrogen sources, such as ammonium ions and nitrates. Azotobacter species have a full range of enzymes needed to perform the nitrogen fixation: ferredoxin , hydrogenase , and an important enzyme nitrogenase . The process of nitrogen fixation requires an influx of energy in
1479-434: The cells can be dispersed or form irregular clusters or occasionally chains of varying lengths. In fresh cultures , cells are mobile due to the numerous flagella . Later, the cells lose their mobility, become almost spherical, and produce a thick layer of mucus , forming the cell capsule . The shape of the cell is affected by the amino acid glycine , which is present in the nutrient medium peptone . Under magnification,
1530-403: The cells show inclusions, some of which are colored. In the early 1900s, the colored inclusions were regarded as "reproductive grains", or gonidia – a kind of embryo cells. However, the granules were later determined to not participate in the cell division . The colored grains are composed of volutin , whereas the colorless inclusions are drops of fat, which act as energy reserves. Cysts of
1581-478: The dark-brown, water-soluble pigment melanin at high levels of metabolism during the fixation of nitrogen, which is thought to protect the nitrogenase system from oxygen. In the presence of some saccharides (such as sucrose and raffinose) while on agar plates, a levan ring can form around the A. chroococcum colony. Research has been carried out into A. chroococcum ' s potential applications in improving crop production. At least one study has so far shown
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1632-416: The enzyme varies between different classes of aldehydes. The overall reaction catalysed by the aldehyde dehydrogenases is: In this NAD(P) -dependent reaction, the aldehyde enters the active site through a channel extending from the surface of the enzyme. The active site contains a Rossmann fold , and interactions between the cofactor and the fold allow for the action of the active site. A sulfur from
1683-489: The form of adenosine triphosphate . Nitrogen fixation is highly sensitive to the presence of oxygen, so Azotobacter developed a special defensive mechanism against oxygen, namely a significant intensification of metabolism that reduces the concentration of oxygen in the cells. Also, a special nitrogenase-protective protein protects nitrogenase and is involved in protecting the cells from oxygen. Mutants not producing this protein are killed by oxygen during nitrogen fixation in
1734-516: The form of cysts for up to 24 years. Representatives of the genus Azotobacter are also found in aquatic habitats, including fresh water and brackish marshes. Several members are associated with plants and are found in the rhizosphere , having certain relationships with the plants. Some strains are also found in the cocoons of the earthworm Eisenia fetida . Azotobacter species are free-living, nitrogen-fixing bacteria; in contrast to Rhizobium species, they normally fix molecular nitrogen from
1785-532: The genus Azotobacter are more resistant to adverse environmental factors than the vegetative cells ; in particular, they are twice as resistant to ultraviolet light. They are also resistant to drying, ultrasound , and gamma and solar irradiation , but not to heating. The formation of cysts is induced by changes in the concentration of nutrients in the medium and addition of some organic substances such as ethanol , n- butanol , or β-hydroxybutyrate . Cysts are rarely formed in liquid media. The formation of cysts
1836-441: The genus Azotobacter is the resting form of a vegetative cell; however, whereas usual vegetative cells are reproductive, the cyst of Azotobacter does not serve this purpose and is necessary for surviving adverse environmental factors. When more favorable environmental conditions resume, which include a certain value of pH , temperature, and source of carbon , the cysts germinate, and the newly formed vegetative cells multiply by
1887-422: The intermediate structures can be toxic, and health problems arise when those intermediates cannot be cleared. When high levels of acetaldehyde occur in the blood, facial flushing, lightheadedness, palpitations, nausea, and general “hangover” symptoms occur. These symptoms are indicative of a medical condition known as the alcohol flush reaction , also known as “Asian flush” or “Oriental flushing syndrome”. There
1938-531: The intima hydrolyses and is used by the cell for the synthesis its components. Azotobacter respires aerobically , receiving energy from redox reactions, using organic compounds as electron donors , and can use a variety of carbohydrates, alcohols , and salts of organic acids as sources of carbon. Azotobacter can fix at least 10 μg of nitrogen per gram of glucose consumed. Nitrogen fixation requires molybdenum ions, but they can be partially or completely replaced by vanadium ions. If atmospheric nitrogen
1989-485: The mobility of heavy metals in the soil, thus enhancing bioremediation of soil from heavy metals, such as cadmium , mercury and lead . Some kinds of Azotobacter can also biodegrade chlorine -containing aromatic compounds , such as 2,4,6-trichlorophenol , which was previously used as an insecticide , fungicide , and herbicide , but later was found to have mutagenic and carcinogenic effects. Owing to their ability to fix molecular nitrogen and therefore increase
2040-413: The most important enzymes for aldehyde oxidation, and both are tetrameric enzymes composed of 54 kDa subunits. These enzymes are found in many tissues of the body but are at the highest concentration in the liver. The active site of the aldehyde dehydrogenase enzyme is largely conserved throughout the different classes of the enzyme and, although the number of amino acids present in a subunit can change,
2091-471: The normal allele, for it shows a higher K m for NAD and has a higher maximum velocity than the wild-type allele. This mutation is common in Japan, where 41% of a non-alcoholic control group were ALDH2 deficient, where only 2–5% of an alcoholic group were ALDH2-deficient. In Taiwan, the numbers are similar, with 30% of the control group showing the deficiency and 6% of alcoholics displaying it. The deficiency
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2142-415: The overall function of the site changes little. The active site binds to one molecule of an aldehyde and one molecule of either NAD or NADP , which functions as a cofactor. Cysteine and glutamate molecules interact with the aldehyde substrate. Many other residues will interact with NAD(P) to hold it in place. Magnesium may be used to help the enzyme function, although the degree to which magnesium assists
2193-524: The shell is called intine and has a fibrous structure. The outer part has a hexagonal crystalline structure and is called exine. Exine is partially hydrolyzed by trypsin and is resistant to lysozyme , in contrast to the central body. The central body can be isolated in a viable state by some chelation agents. The main constituents of the outer shell are alkylresorcinols composed of long aliphatic chains and aromatic rings. Alkylresorcinols are also found in other bacteria, animals, and plants. A cyst of
2244-448: The soil fertility and stimulate plant growth, Azotobacter species are widely used in agriculture, particularly in nitrogen biofertilizers such as azotobacterin . They are also used in production of alginic acid , which is applied in medicine as an antacid , in the food industry as an additive to ice cream, puddings, and creams. The genus Azotobacter was discovered in 1901 by Dutch microbiologist and botanist Martinus Beijerinck, who
2295-420: The soil is fit for crop growth, as it would thrive in soils that have these nutrients. A. chroococcum is also a possible asset for bioremediation. Melanin produced by this bacterium can bind to heavy metals, subsequently protecting A. chroococcum , which may be useful for removing heavy metals from polluted soils. Since this bacterium is able promote plant growth through nitrogen fixation, it can also reduce
2346-485: The soil. In addition to treating soils polluted with heavy metals, A. chroococcum can act as a fungicide that can be used to treat soils and plants inflicted with fungal infections, specifically fungi that are susceptible to "fungicidal substances of the anisomycin group". This bacterium can also be used to determine the nutrient composition of the soil. Since plants and A.chroccoccum both need phosphorus and potassium to grow, this bacterium can be used to determine if
2397-487: The species of Azotobacter nigricans Krasil'nikov, 1949 which was divided in 1981 by Thompson Skerman into two subspecies – Azotobacter nigricans subsp. nigricans and Azotobacter nigricans subsp. achromogenes ; in the same year, Thompson and Skerman described Azotobacter armeniacus Thompson and Skerman, 1981 . In 1991, Page and Shivprasad reported a microaerophilic and air-tolerant type Azotobacter salinestris Page and Shivprasad 1991 which
2448-401: Was dependent on sodium ions. Earlier, representatives of the genus were assigned to the family Azotobacteraceae Pribram, 1933 , but then were transferred to the family Pseudomonadaceae based on the studies of nucleotide sequences 16S rRNA . In 2004, a phylogenetic study revealed that A. vinelandii belongs to the same clade as the bacterium Pseudomonas aeruginosa , and in 2007 it
2499-431: Was discovered and described in 1901 by Dutch microbiologist and botanist Martinus Beijerinck . Azotobacter species are Gram-negative bacteria found in neutral and alkaline soils, in water, and in association with some plants. Cells of the genus Azotobacter are relatively large for bacteria (2–4 μm in diameter). They are usually oval, but may take various forms from rods to spheres . In microscopic preparations,
2550-401: Was one of the founders of environmental microbiology . He selected and described the species Azotobacter chroococcum – the first aerobic , free-living nitrogen fixer. In 1909, Lipman described Azotobacter vinelandii , and a year later Azotobacter beijerinckii Lipman, 1904 , which he named in honor of Beijerinck. In 1949, Russian microbiologist Nikolai Krasilnikov identified
2601-430: Was suggested that the genera Azotobacter , Azomonas and Pseudomonas are related and might be synonyms . Azotobacter chroococcum Azotobacter chroococcum is a bacterium that has the ability to fix atmospheric nitrogen. It was discovered by Martinus Beijerinck in 1901, and was the first aerobic, free-living nitrogen fixer discovered. A. chroococcum could be useful for nitrogen fixation in crops as
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