Enzymology and Catalytic Mechanism

An enzyme is a catalyst since it bears two essential features. First, in a given chemical reaction, an enzyme affects its equilibrium but leaves its rate unaffected. The reaction goes on downhill rather energetically in agreement with the thermodynamics’ second law. The enzyme just lessens the duration required by a reaction, which is favored thermodynamically, to attain its equilibrium state. Notably, the law does not tell the speed with which such a reaction happens. Rather, the law tells of the possibility of the reaction’s occurrence (Jencks, 1987).

Second, an enzyme is a catalyst since it speeds up a given chemical reaction’s rate in the reverse direction and in the forward direction. This actuality stems from the reality that enzymes, and all catalysts in general, are incapable of changing chemical reactions’ equilibriums. At their equilibriums’ the reactions move in the two directions at similar rates.

In the foremost two phases of the liver-based metabolism of fructose, various enzymes serve as protein-based catalysts. The natural sources of fructose include fruits. Fructose undergoes the metabolism to afford body tissues energy. The metabolism’s foremost phase is fructolysis, which occurs within the liver. Fructolysis is a reaction that fructose undergoes resulting in fructose-1-phosphate (Jencks, 1987). The reaction is speeded up by fructokinase, a protein-based catalyst.

The second phase entails a reaction in which glyceraldehyde plus DHA-P (dihydroxyacetone phosphate) is formed from fructose-1-phosphate. Aldolase B, another protein-based catalyst, speeds up the second reaction (Yon-Kahn & Hervé, 2010). The products stemming from the second reaction are utilized by body tissues in subsequent biochemical reactions, which eventually give rise to particular energy-packed molecules, ATPs.

When fructose’s metabolism is underway, aldolase B acts on a particular substrate, fructose-1-phosphate. Fructose-1-phosphate is derived from fructose. When fructokinase acts on fructose, it generates the substrate.

Aldolase B plays a vital role in fructose’s metabolism. The enzyme speeds up an important gluconeogenic-glycolytic channel phase particularly within an individual’s liver, ileum along with renal cortex. When fructose enters the individual’s blood via an absorption process, phosphorylation, which fructokinase speeds up, results into fructose-1-phosphate’s formation.

Subsequently, fructose-1-phosphate enters into a reaction that gives rise to glyceraldehyde plus DHA-P. Subsequently, glyceraldehyde enters into a cycle that gives rise to glyceraldehyde-3-phosphate. The cycle is essentially a reaction, which triose kinase speeds up. Subsequently, glyceraldehyde-3-phosphate enters into a cycle in which it is modified into glucose in many instances or pyruvate in other instances (Yon-Kahn & Hervé, 2010).

Aldolase B’s products can go into diverse pathways. The products are glyceraldehyde plus DHA-P. As noted earlier, glyceraldehyde enters into a cycle that gives rise to glyceraldehyde-3-phosphate. The cycle is essentially a reaction, which triose kinase speeds up. Subsequently, glyceraldehyde-3-phosphate enters into a cycle in which it is modified into glucose in many instances or pyruvate in other instances (Jencks, 1987).

When fructose’s metabolism is underway, aldolase B acts on fructose-1-phosphate. When an individual has below-normal levels of the enzyme, it means that the fructose-1-phosphate in his or her body is not broken down at a regular rate. The amount of the substrate in the individual’s blood keeps on increasing

Aldolase B’s action on fructose-1-phosphate aids prevent HFI (Yon-Kahn & Hervé, 2010). The level of the enzyme in the body is dependant on the efficiency with which the body’s aldolab forms it. The mutation of given aldolab genes compromises its efficiency in the formation of the enzyme. When the body has below-normal levels of the enzyme, it means that the fructose-1-phosphate in his or her body is not broken down at a regular rate. The body is incapable of converting the substrate into glyceraldehyde plus DHA-P (Jencks, 1987).

That means that the body is incapable of completely metabolizing the available molecules of fructose in blood. Fructose-1-phosphate rapidly accumulates in the individual’s liver, as well as ileum, along with kidney. The liver is damaged by the surplus amounts of the substrate. The poor conversion of the substrate means that blood-sugar levels in the body fall speedily. When the liver is damaged, it malfunctions. It gives rise to hypoglycemia plus HFI.

In theory, when the switch of a Cori cycle takes place in a given cell, it gives rise to a cycle commonly christened FC (futile cycle). Basically, the given cell utilizes and as well re-synthesizes the cycle’s glucose rather than executing GTP hydrolysis plus ATP hydrolysis (Jencks, 1987).

            Essentially, when the CAC is underway, limited energies that are released lead to the generation of ATPs. CO2 molecules are generated in the chain via which electron are transported. The production of the CO2 molecules subsequently leads to the formation of molecules of oxaloacetic acid (Yon-Kahn & Hervé, 2010). Each of the molecules of oxaloacetic acid has four atoms of carbon. Within the CAC, a theoretical enzyme defect occurring in the functional areas acted upon by ATP synthase would lessen mitochondria’s production of ATP. ATP synthase is a protein-based catalyst.

Every defect in the chain surely compromises, or stalls, the conversion of ADPs into ATPs. Elementarily, the chain grows a slope. The slope aids in ATP synthase’s production. That portends that every defect in the chain stalls the formation of ATPs via ADPs’ conversion. Notably, the products of CAC, succinate plus NADH, enter reactions that result into ATPs. The reactions involve oxidative-phosphorylation within mitochondria. The oxidation of succinate plus NADH generates energy. The energy powers the enzyme, enabling it to support the production of ATPs (Jencks, 1987).

Q10, a co-enzyme, plays a particular role in chains via which electrons are transported. The co-enzyme is a vitamin. It aids the production of ATPs or energy in living cells. Q10 is markedly ubiquitous, or common. It supports the transformation of carbohydrates plus fats into energy molecules with mitochondria’s inner membranes. It accepts, as well transforms, the electrons that are given off in the metabolism of glucose plus fatty acids. It accepts, as well transforms, the electrons into unique electron acceptors. Concurrently, it pushes protons out of the mitochondria’s inner membranes. That creates proton slopes, or gradients, in the protons. Such slopes force the protons to shift within the membranes, giving off ATPs.

The synthesis of ATPs is not thermodynamically favorable as a reaction. Its occurrence requires energy, which is sourced from NADH’s oxidation plus FADH2’s oxidation. The two are oxidized by four complexes of the ETC (electron transport chain). Such complexes are protein based. The NADHs enter the ETC from various processes: glycolysis, the CAC, and pyruvate’s conversion into acetyl-CoA. The FADH2s enter the ETC from the CAC. The ETC’s events involve FADH along with NADH, with both transporting electrons as they move through the membrane (Jencks, 1987).

In the first of the four complexes, electrons move from given NADH to the ETC and onwards to the second, third, as well as fourth, complexes. The second of the four complexes oxidizes given FADH, getting extra electrons for the ETC. In the third of the four complexes, the ETC does not get extra electrons. Even then, the complex has electrons from the preceding complexes flowing all the way through it. The electrons at the fourth complex are moved to given oxygen molecules, reducing them to water (Yon-Kahn & Hervé, 2010). As the electrons moves across the four complexes, they pump protons into cells’ cytosols. Accordingly, negative charges accumulate in the attendant matrix spaces and positive ones accumulate in the attendant inter-membrane spaces. The charges occasion differentials that are essentially electrochemical gradients. Such gradients drive the synthesis of ATPs within the process known as oxidative phosphorylation.

In oxidative phosphorylation, ATPs are formed from phosphates and ADPs in mitochondria’s matrixes. The formation is speeded up by the PT (proton-translocating) ATP synthase, which is the protein element in the fourth complex. The electrochemical gradients across the inside membranes of mitochondria allow protons to move across such membranes via unique channels regulated by ATP synthase. The enzyme utilizes the generated energy by the transport that is thermodynamically sympathetic to convert phosphates plus ADPs into ATPs (Jencks, 1987).

 

 

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