Glycolytic pathway

IV. type is mainly present in the liver, specially known as glucokinase (glucokinase, GK), the Km value of glucose 1 to 10-2M, normal The blood sugar concentration is 5mmol/L, when the blood sugar concentration increases, GK activity increases, glucose and insulin can induce the liver to synthesize GK, GK can catalyz glucose, glycerides to produce its 6-phosphate, 6-phosphate glucose has no inhibitory effect on this enzyme.

< the difference between HK and GK > 4-1 in the form of a p class of "tt1". < the difference between >p align"center" class"biaotou" table 4-1 hetose kinase (HK ><) and glucose kinase (GK< td align> "middle" GK< "middle" > tissue distribution<β >< > km low high6- phosphate glucose inhibition< "middle" > have < class -"tt1" >(2)6-isomer reaction of phosphate glucose (isomeration of glucose-6-phosphate)

this is catalyzed by phosphohex isomerase 6-phosphate glucose (aldes. The process of transitioning to 6-phosphate fructose (fructose-6-phosphate, F-6-P) is reversible.

< p-align>< "center" >

(3) 6-phosphate fructose phosphorylation (phosphorylation of fructose-6-phosphate)

this reaction is 6 phosphate fructose first on the C further phosphate to produce 1,6-phosphate fructose, phosphoric acid root is supplied by ATP, catalyzed this reaction is phosphorus fructose kinase 1 (phosphofructokinase l, PFK1).

PFK1 catalytic reaction is irreversible, it is the most important speed limit enzyme in the aerobic oxidation process of sugar, it is also a variant enzyme, citric acid, ATP, etc. are variant inhibitors, ADP, AMP, Pi, 1,6-phosphate fructose, etc. are variant activators, insulin can induce its generation.

(4) 1.6 diphosphate fructose lysate reaction (cleavage of fructose 1,6 di/bisphosphate)

aldolase catalyzed 1.6-dephosphate fructose to produce phosphate hydroxypropylone and 3-phosphate glycerol, this reaction is reversible.

< isomer reactions to >< p-class-tt1" >(5) hydroxyhydroxyacetone (isomerization of dihydroxyacetonephosphate)

propylene phosphate isomerase catalyzed phosphate acetone into 3-phosphate glycerol, this reaction is also reversible.

to this 1 molecule glucose to produce 2 molecules 3-phosphate glycerides, through twice phosphate action to consume 2 molecules ATP.

2. Phase 2:

(6) 3-oxidation reaction (oxidation of glyceraldehyde-3-phosphate

this reaction is by 3-phosphate glycerides< "> dehydrogenase (glyceraldehyde 3-phosphedatedehydrogenase) catalyzed 3-phosphate glycerides oxidized dehydrogenation and phosphate to produce a high-energy phosphoric acid bond containing 1,3-diphosphate glyphosate, the reaction of hydrogen and electron transfer to dehydrogenase coenzyme NAD plus the generation of NADH plus H, phosphoric acid root from the non-machine phosphoric acid.

(7) 1.3-glyphosate high-energy phosphoric acid key transfer reaction

in phosphatlytase (phosphaglycerate kinase, PG K) catalytically, 1.3-dipphosphate glyceric acid produces 3-phosphate glyceric acid, while the high-energy phosphoric acid root on C1 is transferred to ADP to generate ATP, the energy generated during the oxidation process of this substrate directly produces ATP process of ADP phosphorylation, called substrate level phosphorylation (substrate levelphosphorylation). The catalytic reaction of this kinase is reversible.

(8) 3 - Phosphate glyceric acid variant reaction

< p class "tt1" > the phosphoric acid glycerate metastase (phosphoglycerate mutase) catalyzed 3-phosphoric glycerate C3-bit phosphoric acid to the C2 bit to produce 2-phosphate glyceric acid. This reaction is reversible.

(9) 2 - Dehydration reaction of glyphosate

Enolase catalysis, 2-phosphate glyphosate dehydration at the same time, energy redistribution, the production of high-energy phosphoric acid bonds phosphool acetone acid (phosphoenolpyruvate PEP). The reaction is also reversible.

(10) phosphate transfer

at the catalysis of acetone kinase (pyruvate kinase, PK), high-energy phosphate roots on phosphate alcohol-type acetone acid are transferred to ADP to produce ATP, another phosphate process at the substrate level. But this reaction is irreversible.

acetone acid kinase is a speed limit enzyme in the aerobic oxidation process of sugar, with variant enzyme properties, AT P is a variant inhibitor, ADP is a variant activator, Mg2 plus or K plus can activate the activity of acetone kinase, insulin can induce PK production, oleol acetone acid can be automatically converted into acetone acid.

sums up the oxygen-free enzyme solution of sugar In the process of cell fluid phase, a molecule of glucose or a glucose unit in the glycogen, oxidation and decomposition produces 2 molecules of acetone acid, acetone acid will enter mitochondrial continue oxidation and decomposition, the process of producing two For NADH-H-plus, the transfer of hydrogen body α-phosphate glycelin (muscle and nerve tissue cells) or apple acid (myocardial or liver cells) is transmitted into the mitochondrial, and then through the transmission of oxidized respiratory chains in the mitochondrial body, and finally hydrogen and oxygen bind to produce water, which is released in the hydrogen transfer process, some of which is stored in the form of ATP.

< in the whole cell fluid stage of 10 or 11 steps > enzymatic reaction, in physiological conditions, there are three steps irreversible one-way reaction, catalytic reaction of the enzyme activity is low, is the key enzyme of the oxygen oxidation process of the whole sugar, its active size, the oxidation and decomposition rate of sugar plays a decisive role in this stage by the substrate level phosphate to produce four molecules ATP.

Figure 4-2 glucose decomposition of the two stages

In summary, through the glycolysis process, a molecular glucose oxidation and decomposition to produce 2 molecules of acetone acid. In this process, the substrate level phosphatation can produce 4 molecules ATP, such as phosphate consumption of phosphate consumption with the first stage of glucose phosphate attainment of the two molecules ATP offset each other, each molecular glucose degradation to acetone acid net production of 2 molecules ATP, such as from the beginning of the glycogen, because the beginning stage consumes only 1 molecule ATP, so each glucose unit can net produce 3 molecules ATP (Figure 4-2). Glucose plus 2Pi plus 2NAD plus 2ADP→2 acetone acid plus 2ATP plus 2NADH plus 2H2O

(iii) acetoneic acid produces lactic acid under oxygen-free conditions. <