Aerobic oxidation of sugar.

calledglucose under aerobic conditions, the process of oxidation and decomposition to produce carbon dioxide and water is called aerobicoxidation. Aerobic oxidation is the main way of sugar decomposition metabolism,
glucose
in most tissues is oxygen oxidized and decomposed to supply the body's energy.(i) Aerobic oxidation processaerobic oxidation of sugar is carried out in two stages. The first stage is acetone acid produced by glucose, which is carried out in cell fluid. The second stage is the above-mentioned process of NADH plus H and acetone acid in the aerobic state, into the mitochondrial, acetone acid oxidation dehydrate to produce acetylCoA into the triamlic acid cycle, and then oxidation to produce CO2 and H2O, while NADH plus H plus can be transmitted through the respiratory chain, along with phosphorylation process to produce H2O and ATP, the following will mainly discuss the oxygen oxidation mitochondrial metabolism.. 1. Oxidizing dehydrogenation of acetone acidCatalytic oxidation dehydrogenase enzyme is acetone acid
dehydrogenase
system), this multienzyme complex contains acetone deoxygenase, coenzyme is TPP, dihydrothionic acid Acetyl
transferase
, coenzyme is dihydrothionic acid and coenzyme A, as well as dihydrothionate dehydrogenase, coenzyme is FAD and exists in mitochondrial substation fluid NAD plus, polyenzyme complex formed a closely linked chain reaction mechanism, improve catalytic efficiency.from acetone acid to acetylCoA is a key irreversible reaction in the aerobic oxidation of sugar, the acetone acid dehydrogenase system that catalyses this reaction is affected by many factors, the product of the reaction, acetylCoA and NADH plus H. can inhibit enzymes respectively. The activity of dihydrothionate acetyl transferase and dihydrothionate dehydrogenase in the system, pyruvate decarboxylase (PDC) activity is activated by ADP and insulin, inhibited by ATP.characteristic of the dehydrogenation reaction of acetone acid is that the free energy released by oxidation of acetoneic acid is stored in the high-energy thioester bonds in acetylCoA and produces NADH plus H.. 2. Tricarboxylic acid cycleacetylCoA enters a circular system consisting of a series of reactions, oxidized to produce H2O and CO2. Since this cyclic reaction begins with the contraction of acetylCoA with oxaloacetic acid, which contains three carpentrates, it is called the triacetic acid cycle or citric acid cycle. The detailed process is as follows: (1) acetylCoA enters the triacetic acid cycle acetylCoA has a thioester bond, acetyl base has enough energy to shrink with the acetyl acetic acid carbide-type. First of all, from the CH3CO base to remove an H-plus, the resulting anions on the acetylic acid carbide carbon to carry out a nuclear attack, the generation of citricylCoA intermediates, and then high-energy sulfuric acid key water to free free free citric acid, so that the reaction irreversibly to the right. This reaction is catalyzed by citrate synthetase and is a strong energy release reaction.
Synthesized citric acid by oxalic acid and acetylCoA is an important regulatory point of the triacetic acid cycle, citric acid synthase is a variant enzyme, ATP is a variant inhibitor of citric acid synthase, in addition, α-ketone diacid, NADH can inhibit its activity, long-chain lipid coA can also inhibit its activity, AMP can fight the inhibition of ATP and activate.(2) isocitric acid formation citric acid's serpenol base is not easy to oxidize, into isocitric acid and make sci-acid into a midol, it is easy to oxidize, this reaction is catalyzed by shun-head acidase, for a reversible reaction.(3) First oxidation deacidationUnder the action of iso-citric acid dehydrogenase, iso-citric acid isool oxidized into carbide, producing oxalosuccinate intermediate product, The latter, on the same enzyme surface, rapid dehydration produces α-ketoglutarate, NADH, and CO2, a reaction of β-oxidizing dehydrate, which requires Mn2 plus as an activator.this reaction is irreversible and is a speed-limiting step in the triacetic acid cycle, where ADP is the activator of isocitric acid dehydrogenase, and ATP, NADH, is the inhibitor of this enzyme.(4) Second oxidation dehydrogenationUnder the action of α-ketone dihydrogenase system, α-ketone dihydrogenic acid oxidation dehydrogenation produces amber CoA, NADH plus H and CO2, the reaction process is exactly similar to acetone dehydrogenase system catalytic oxidation dehydrogenation α, a part of the energy produced by oxidation is stored in amber CoA high-energy sulfur. the α-ketone dihydrogenase system is also composed of three enzymes (α-ketone diacidase, sulphate amberyl transferase, dihydrothionic acid dehydrogenase) and five coenzymes (TPP, thiopic acid, HSCoA, NAD plus, FAD). this reaction is irreversible. α-ketone dihydrogenase complex is inhibited by ATP, GTP, NAPH, and amber coA, but is not regulated by phosphorylation/dephosphorylation. (5) substrate phosphatization produces ATP in the role of sulfuric acid
kinase
(succinate thiokinase), the hydrolytics of the thioester keys of amber CoA, the release of free energy for synthesis of GTP, in bacteria and advanced organisms can directly generate ATP, in mammals, Mr. GTP, and then produce ATP, at this time, amber CoA to produce amber acid. (6) succinate dehydrogenation succinate dehydrogenase catalyzed amber acid oxidation into Yanhuso acid. The enzyme binds to the membrane of the mitochondrial membrane, while the other triacetic acid cycle enzymes are present in the mitochondrial substate, which contains iron sulfur center and co-price binding FAD, electrons from amber acid through THE and iron sulfur center, and then into the electron transfer chain to O2, propylene diacid is a similar to amber acid, is a strong competitive inhibitor of sulphate dehydrogenase, so it can block the triacetic acid cycle. (7) Hydration of Yanhuso acid Yanhuso acidase only works on the reverse double bonds of Yanhuso acid, while shunbutyl disic (Malay acid) has no catalytic effect and is therefore highly stereoscopic. (8) oxyacetic acid regeneration Under the action of malic deogenhydrase, malic deogenhydrase, malic dehydrogenation is oxalocate, which produces oxalocetate, a coenzyme of NAD plus dehydrogenase, which accepts hydrogen as NADH plus H plus (Figure 4-5). summary of the cycle of acetylCoA, 3NADH, FAD, GDP, Pi, 2H2O- →2CO2, 3NADH, FADH2, GTP, 3H, coASH (1) CO2 generation, two degeneration reactions in the cycle (reaction 3 and Reaction 4) both times have dehydrogenation, but the action of different agents, catalyzed by isocitric acid dehydrogenase β oxidizing dehydrogenation, coenzyme is NAD-plus, they first dehydrogenate the substrate to produce oxalic acid, and then in collaboration with Mn2 plus or Mg2 plus, de-dehydrogenation, the generation of α-ketone diacid. α reactions catalyzed by the acetone α-ketone dihydrogenase system and the aforementioned acetone acid dehydrogenase system are essentially the same. it should be pointed out that the generation of CO2 by dehydration is a common law of CO2 production in the body, which shows that the generation of CO2 in the body is very different from the process of generating CO2 by in vitro combustion. (2) four dehydrogenations in the trihydric acid cycle, three pairs of hydrogen atoms with NAD plus as hydrogen, and one pair with FAD as hydrogen, respectively, reduced to produce NADH plus H plus and FADH2.
They are then transmitted by a hydrogen delivery system in the mitochondrial body, which eventually binds to oxygen to generate water, and the energy released in the process enables ADP and Pi to combine to produce ATP, where NADH plus H plus participates in the hydrogen delivery system, oxidizing each 2H into a molecule H2O, generating 3 molecules ATP.
the hydrogen delivery system in which FADH2 is involved produces 2 molecules ATP, plus a single substrate phosphorylation in the tricetaric acid cycle produces a molecule ATP, then a molecule CH2COSCoA participates in the tricetamic acid cycle until a total of 12 molecules ATP is generated at the end of the cycle. (3) acetylcoA carbon atom, acetylCoA enters the cycle, shrinks with the four carbon subject molecule grass acetic acid, produces six carbon citric acid, in the triacetate cycle there is a secondary decarbonization to produce 2 molecule CO2, with the number of carbon atoms entering the cycle, but the carbon lost in CO2 is not from the two carbon atoms of the acetylyl, but from acetylate. (4) the intermediate product of the triacetic acid cycle, in theory, can not be consumed in the cycle, but because some components of the cycle can also participate in the synthesis of other substances, and other substances can also continue to generate intermediate products through a variety of ways, so the composition of the tricarbonate cycle is constantly updated. e.g. glyphosate acetic acid - → tianmen dongeine α- ketone diacid - → glutamate oxaltamate - → acetone - → acetaminophen where the reaction to oxaltaminase catalysis is the most important. because of the content of grass acetic acid, directly affect the speed of circulation, so constantly supplementing grass acetic acid is the key to the smooth progress of the triacetic acid cycle. and oxalacetic acid produced in the triacetic acid cycle can also be dehydrated to produce acetone acid, which is then involved in the synthesis of many other substances or further oxidation. (ii) Physiological significance of aerobic oxidation of sugar the cycle of triamlic acid is the main way for the body to obtain energy. 1 molecule glucose by anaerobic enzyme only net production of 2 molecules ATP, while aerobic oxidation can net production of 38 ATP (e.g. Table 4?), of which the triglyceric acid cycle to produce 24 ATP, in general physiological conditions, many tissue cells from the aerobic oxidation of sugar to obtain energy. The aerobic oxidation of sugar is not only efficient, but also gradually released and stored in ATP molecules, so the utilization rate of energy is also very high. . 2. Triacetic acid cycle is sugar, fat and
protein
three major organic matter in the body thoroughly oxidized the common metabolic pathway, triacetic acid cycle of the starting acetyl coenzyme A, not only sugar oxidation and decomposition products, it can also come from the fat glyce. Oils, fatty acids, and certain
amino acids
metabolized from proteins, so the triacetic acid cycle is actually a common path of oxidation and energy supply from the three main organic matter in the body, and it is estimated that two-thirds of the organic matter in the human body is broken down by the triacetonic acid cycle. . 3. Triacetic acid circulation is the intervulation mechanism of the three main organic matter in the body, because sugar and glyceel metabolism in the body can produce α-ketone diacic acid and oxalic acid and other intermediate products of triacetic acid cycle, these intermediate products can be transformed into certain amino acids;
And some amino acids can be turned into α-ketone diacate and oxalacetic acid in different ways, and then produced by sugar isogenated or converted into glyceros, so the triamlic acid cycle is not only the final common way for the three main organic matter to break down metabolism, but also their mutually variable contact mechanism. (iii) Regulation of sugar aerobic oxidation As mentioned above, the regulation of sugar aerobic oxidation is divided into two stages, the regulation of the first stage of sugar enzymeization pathway has been discussed in the sugar enzyme part, the following main discussion is mainly discussed in the second stage of acetate oxidation to produce acetylCoA and enter the triacetic acid cycle of a series of reactions. Acetone dehydrogenase complex, citric acid synthase, isocric acid dehydrogenase and α-ketone dihydrogenase complex are the speed limit enzymes for this process. Acetone dehydrogenase complex is also regulated by chemical modification, the enzyme complex by its catalytic products ATP, acetylCoA and NADH strong inhibition, this other position inhibition can be enhanced by long-chain fatty acids, when entering the triacetic acid cycle acetylCoA decreased, and AMP, coenzyme A and NAD-plus accumulation, the enzyme complex is activated by the other.
In addition to the above-mentioned other-position regulation, in vertebrates there is a second level of regulation, that is, the chemical modification of enzyme proteins, PDH contains two sub-base, one of which is a specific serine residue by phosphorylation, enzyme activity is inhibited, dephosphorylation activity is restored, phosphorylation-dephosphorylation is determined by the specific
phosphate kinase and phosphorylase
respectively.
They are also actually the composition of the acetone enzyme complex, that is, the previously mentioned regulatory protein, kinase is activated by ATP, when ATP is high, PDH is activated on phosphate, when ATP concentration decreases, kinase activity is also reduced, and phosphatase removes PDH phosphoric acid, PDH is activated. The regulation of citric acid synthase, isocitric acid dehydrogenase and α-ketone dihydrogenase in the triacetonic acid cycle is mainly achieved through feedback inhibition of the product, and the tricelic acid cycle is the main way of the body's production capacity.
the ratio of ATP/ADP to NADH/NAD plus is the main regulator. The ATP/ADP ratio increases, inhibits the activity of citric acid synthase and iso-citricase dehydrogenase, and the ATP/ADP ratio decrease activates both enzymes. < br.