Enzymes are like "Spring-Loaded bear-traps" ?

[Widdekind]

Allegation (?): Enzymes are "spring-loaded", storing Mechanical Potential Energy (MPE). When an enzyme binds with a reactant, the "spring-loaded catch-mechanism" is tripped, "trapping" the reactant into the enzyme's active binding site. This "clamping" process imparts the enzyme's stored MPE into the chemical bonds of the reactant, thereby supplying some significant fraction of the Activation Energy (AE) required to run the relevant chemical reaction (MPE --> AE). Then, the "clamped" reactants bind, into their new chemical combination, which has allot lower total energy. So much energy is released, in their (exergonic) reaction (RE), that the new chemical compound "jerks free & loose" from the enzyme, "kicking open" the enzyme's chemo-mechanical "clamp", resetting the "trap", and re-imparting the requisite MPE to do so (RE --> MPE + excess).

 

Enzymes are proteins that function as highly selective biological catalysts... Unlike non-biological catalysts, each enzyme typically catalyzes only a single reaction. Enzymes have sites that bind to one or more of the reactants of the reaction [that] they catalyze. A reactant that binds to an enzyme is called the substrate of that enzyme, and the place on the enzyme where the substrate binds is called the active site...

 

The way that enzymes interact with their substrates is often analogized to the physical relationship between a lock & key. However, the physical structure of an enzyme is not necessarily rigid, in the way an actual lock & key are. In many cases, the interaction of a substrate w/ an enzyme causes the active site of the enzyme to change shape, allowing the substrate to fit even more snugly into position.

 

This more dynamic view of the physical interaction between an enzyme and its substrate is called the induced-fit model, b/c the substrate induces a tighter fit, by causing the enzyme to change its shape slightly. This tighter fit brings the chemical groups associated with the active site even closer to help catalyze the reaction.

 

Once a substrate binds to the active site of an enzyme, the active site catalyzes the conversion of this substrate into the reaction's product, which drops off the enzyme...

 

[A] common way for enzymes to catalyze reactions, is by imposing additional molecular stresses on the substrate. As the substrate & active site bind together, the enzyme changes its shape, [and] the active site of the enzyme may affect the shape of the substrate, as well. This shape change puts more tension on the molecular bonds of the substrate, making them less stable, and allowing them to be broken more easily.

 

[Teaching Company -- Great Courses] Biology: Science of Life, Lecture 51

[steevey]

Allegation (?): Enzymes are "spring-loaded", storing Mechanical Potential Energy (MPE). When an enzyme binds with a reactant, the "spring-loaded catch-mechanism" is tripped, "trapping" the reactant into the enzyme's active binding site. This "clamping" process imparts the enzyme's stored MPE into the chemical bonds of the reactant, thereby supplying some significant fraction of the Activation Energy (AE) required to run the relevant chemical reaction (MPE --> AE). Then, the "clamped" reactants bind, into their new chemical combination, which has allot lower total energy. So much energy is released, in their (exergonic) reaction (RE), that the new chemical compound "jerks free & loose" from the enzyme, "kicking open" the enzyme's chemo-mechanical "clamp", resetting the "trap", and re-imparting the requisite MPE to do so (RE --> MPE + excess).

 

 

 

Ok, here's how enzymes work. They have a special shape and special chemical properties for two or more chemicals. Normally when you mix two reactants together, on a molecular level its random if the molecules come into contact with each other to bond. What an enzyme does is take both of those reactants and combines them for you. Enzymes just speeds the process of the reactants forming new chemicals, more like this.

 

 

 

 

Then, after the chemicals are bonded, they are no longer attached the to enzyme, so the enzyme can now bond two more.

Edited December 19, 2010 by steevey

[mississippichem]

For clarity, I feel I should add that most enzymes have an active site that is "tailor-fitted" for the transition state of the substrate with respect to the intended reaction instead of the substrate itself. If the enzyme fits the substrate perfectly, there would likely be little chemical potential for the substrate to undergo the transformation. Read about Michaelis-Menten kinetics or transition state theory for a more rigorous explanation.

[Widdekind]

When Enzymes "latch onto" their particular Substrate molecules, there is a "distortion of the bonds in the Substrate, which occurs on binding; these bonds, now under strain, are more readily broken" ([Open University -- S104, Bk. 5] Life, p.94). Thus, Electro-Mechanical Potential Energy (EMPE), latent in the "unsprung" Enzyme, is applied to electron bonds in the Substrate molecule, physically stretching out those electrons' Molecular Bonding Orbitals (MBOs), and thereby "partially breaking" those bonds, raising their EMPE, and making them easier to break:

 

[math]EMPE_{enzyme} \rightarrow EMPE_{substrate}[/math]

To wit, Enzymes transfer latent "unsprung" EMPE, to their specific Substrates, upon being "sprung", by binding with the same. This "Energy effect" happens in addition to the "spatial positioning effect", per PPs by Steevey & Mississippichem. When, boosted by both physical phenomena, the various Substrates are assembled into the final reaction Product, that Product, by "pulling its pieces together", re-stresses the electron bonds of the Enzyme's Binding Sites, "pulling the traps back open", and so "re-setting" the same, into their "unsprung" states. To wit, the Product molecule transfers EMPE back to the Enzyme:

 

[math]EMPE_{enzyme} \rightarrow EMPE_{substrates}[/math]

 

[math]\Sigma s_i \rightarrow P[/math]

 

[math]EMPE_{product} \rightarrow EMPE_{enzyme}[/math]

Electron bonding orbitals possess spring-like EMPE, so that stressing & stretching the same requires, and stores, Work Energy. EMPE, latent in the "unsprung" Enzyme, does Work on Substrate bonds. Then, as it assembles, the Product does Work on the "sprung" Enzyme bonds, "popping the traps [binding Sites] back open", and returning the Enzyme to its "unsprung" state.