Name: diffusion-controlled enzymes and reaction speed
Uploaded: 2023-04-30T10:09:49.000Z
Duration: 1 min 7 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.1.2

Catalytically Perfect Enzymes

촉매적으로 완벽한 효소는 높은 회전율, kcat 및 기질에 대한 강한 친화도(KM. )로 최대 촉매 효율을 갖습니다.
 
kcat 대 KM 비율은 촉매 효율을 측정합니다. 촉매적으로 완벽한 효소의 경우 이 값의 범위는 초당 몰 기질당 108에서 109까지입니다. 
 
기질 확산은 분자 운동에 의해 발생하는 기질 분자의 지속적인 움직임입니다. 기질은 효소와 상호 작용하기 위해 세포 내에서 확산되어야 합니다. 
 
촉매적으로 완벽한 효소의 반응 속도는 활성 부위로의 기질 확산 속도 또는 활성 부위로부터의 산물 방출 속도에 의해서만 제한됩니다. 일부 효소는 기질을 활성 위치로 끌어당기고 안내하는 정전기력을 통해 촉매 완성도를 달성했습니다. 
 
촉매적으로 완벽한 효소에서 모든 효소-기질 충돌은 빠르게 산물로 변형되는 중간체를 생성합니다.

<ol>
	<li>Ahern, K., & Rajagopal, I. (2021년 3월 6일). 완벽한 효소. 오레곤 주립 대학. https://bio.libretexts.org/@go/page/3036.</li>
	<li>페터슨, G. (1992). 효소의 촉매 효율의 진화적 최적화. 유럽 생화학 저널, 206(1), 289-295.</li>
	<li>Bar-Even, A., Milo, R., Noor, E. 및 Tawfik, DS (2015). 적당히 효율적인 효소 : 헛된 만남과 효소 플로피. 생화학, 54(32), 4969-4977.</li>
</ol>

촉매적으로 완벽한 효소

촉매적으로 완벽한 효소 이론은 1976년 W.J. 앨버리와 J.R. 놀리스에 의해 처음 제안되었습니다. 이 효소는 생화학 반응을 고속으로 촉매합니다. 촉매 효율 값의 범위는 108-109 M-1s-1입니다. 촉매작용의 유일한 속도 제한 단계는 기질이 활성 부위로 확산되는 단계이므로 이러한 효소는 '확산 제어'라고도 합니다. 예로는 삼당 인산 이소머라제, 푸마라제, 슈퍼옥사이드 디스뮤타제가 있습니다.

대부분의 효소는 기질을 활성 부위로 방향을 지정하고 조종하는 표면에 존재하는 전하를 띤 그룹으로 인해 촉매 완벽성을 달성합니다. 일부 다른 효소는 특정 활성 부위 배열을 갖고 있어 촉매 완벽성에 기여합니다. 과산화물 디스뮤타제와 같은 효소에서는 활성 부위에 있는 구리, 아연과 같은 금속 이온과 활성 부위에 가까운 아르기닌과 같은 전하를 띤 아미노산이 과산화물 음이온이 산소와 과산화수소로 전환되는 속도를 높입니다. 효소의 무작위 돌연변이는 기질과의 상호작용을 선호하며 시간이 지남에 따라 효율성이 더 높은 효소가 자연적으로 선택됩니다.

완벽한 효소는 매우 효율적인 반응을 촉진할 뿐만 아니라 유해한 반응 중간체로부터 세포를 보호하는 데도 도움이 됩니다. 예를 들어, 삼당 인산 이소머라제(TPI)는 디히드록시아세톤 인산염(DHAP)과 글리세르알데히드 3-인산염(G3P)의 상호전환을 촉매하는 해당과정 경로의 효소입니다. DHAP가 G3P로 천천히 전환되면 결국 독성 화합물로 분해되는 엔디올 중간체가 형성됩니다. TPI는 촉매적으로 완벽한 효소이기 때문에 반응 속도를 높이고 중간체를 신속하게 제품으로 변환하여 바람직하지 않은 화합물을 방지합니다. 지금까지 촉매적으로 완벽하게 진화한 효소는 거의 없습니다. 대부분의 효소는 적당히 효율적입니다.

촉매적으로 완벽한 효소 이론은 1976년 W.J. Albery와 J. R. Knowles에 의해 처음 제안되었습니다. 이 효소는 다음에서 생화학 반응을 촉매합니다.

Education

교육

JoVE Core

Cell Biology

세포생물학

Unit 1

제1단원

Energy and Catalysis

에너지 및 촉매

KEY TERMS AND CONCEPTS

주요 용어 및 개념

diffusion-controlled enzymes and reaction speed

Catalytically perfect enzymes are enzymes that speed up biochemical reactions at very high rates. The idea was first proposed by W. J. Albery and J. R. Knowles in 1976. These enzymes have catalytic efficiency values of about 10^8 to 10^9 M^-1 s^-1 and are also called diffusion-controlled enzymes because diffusion of the substrate into the active site is the only rate-limiting step.

Examples of catalytically perfect enzymes include triose phosphate isomerase, fumarase, and superoxide dismutase. In many cases, charged groups on the enzyme surface help orient and steer the substrate into the active site. Some enzymes also depend on a specific active site arrangement, which supports this very fast catalysis.

Superoxide dismutase shows how the active site can increase reaction speed. In this enzyme, metal ions such as copper and zinc work with charged amino acids like arginine near the active site. Together, they speed the conversion of superoxide anion into oxygen and hydrogen peroxide.

Catalytic perfection can also arise through natural selection. Random mutations may favor enzyme-substrate interactions, and enzymes with higher efficiency can be selected over time. Even so, only a few enzymes have evolved to this level, and most enzymes are only moderately efficient.

These enzymes can also protect cells from harmful reaction intermediates. Triose phosphate isomerase, or TPI, works in the glycolytic pathway and converts dihydroxyacetone phosphate, or DHAP, into glyceraldehyde 3-phosphate, or G3P. If DHAP changes too slowly, it forms an enediol intermediate that can break down into a toxic compound. Because TPI is catalytically perfect, it rapidly drives the reaction forward and helps prevent unwanted products.

Diffusion-Controlled Enzymes and Reaction Speed

diffusion-controlled-enzymes-reaction-speed

the first law of thermodynamics

Energy Changes in Cells and Matter

The first law of thermodynamics describes how energy changes form in the universe. The total amount of energy stays constant. Energy can move from one place to another or change into a different form, but it cannot be created or destroyed. These energy changes happen in everyday life. A light bulb changes electrical energy into light energy. A gas stove changes chemical energy in natural gas into heat energy. Plants also carry out a major energy transformation when they convert sunlight energy...

the second law of thermodynamics

Entropy and Spontaneous Change

Entropy helps predict whether a process will happen on its own. Entropy is a measure of randomness or disorder in a system. High entropy means high disorder and low energy. A student’s bedroom is a simple example. If no work is done, the room becomes messy over time. That messy state is highly disordered and has high entropy. To make the room clean again, energy must be added as the student puts things away. That organized state has low entropy. Processes that increase the entropy of the...

enthalpy within the cell

Cellular Enthalpy and Energy Changes

Cellular enthalpy describes how heat and energy change during chemical and physical processes. Enthalpy is written as H and is defined as the sum of a system’s internal energy, U, and the product of pressure and volume, PV. It is a state function, which means its value depends on the state of the system, not the path taken. Scientists cannot measure the enthalpy of a single substance directly. They can determine enthalpy changes, or ΔH, for a process instead. For reactions or changes that...

entropy within the cell

Cell Energy Loss and Entropy

Cell energy loss and entropy explain why living things need constant energy input. Cells obtain energy, transform it, and use it to do work, but these transfers are never completely efficient. In each transfer, some energy is lost in a form that cannot be used. In many cases, that lost energy is heat energy.

an introduction to free energy

Gibbs Free Energy and Reaction Work

Gibbs free energy describes the usable energy in a chemical reaction. It helps scientists compare how much energy different reactions release. This measurement is called Gibbs free energy, or G, after Josiah Willard Gibbs. The second law of thermodynamics explains why not all energy stays available for work. Some energy is lost in an unusable form, such as heat, and this loss increases entropy. Gibbs free energy is the energy left after that entropy loss is taken into account. Every chemical...

endergonic and exergonic reactions in the cell

endergonic-and-exergonic-reactions-in-the-cell

Cell Reactions That Release or Store Energy

Cell reactions can either release energy or store it for later use. In chemistry, this difference is described by the value of ΔG, or free energy change. When energy is released during a reaction, ΔG is negative. The products then have less free energy than the reactants because some free energy has been given off. Reactions with a negative ΔG are called exergonic reactions. Exergonic means energy is leaving the system. These reactions are also called spontaneous reactions because they can...

the equilibrium binding constant and binding strength

the-equilibrium-binding-constant-and-binding-strength

How Equilibrium Binding Constant Affects Binding

The equilibrium binding constant describes how strongly two molecules bind at equilibrium. It is a useful way to compare binding strength in molecular interactions. This topic focuses on how binding is measured and what the equilibrium binding constant means. A higher value indicates stronger binding, while a lower value indicates weaker binding. Understanding this constant helps explain how tightly molecules stay together under equilibrium conditions. The page also connects the binding...

free energy and equilibrium

Free Energy and Reaction Direction

Free energy and reaction direction are linked in chemical equilibrium. A free energy change, ΔG, shows the driving force for a process. When ΔG is negative, the process is driven forward. When ΔG is positive, the reverse direction is favored. When ΔG is zero, the forward and reverse driving forces are equal, and the system is at equilibrium. The reaction quotient, Q, helps show how close a system is to equilibrium. Q is the numerical value of the mass action expression for the system. It can...

non-equilibrium in the cell

Cells Stay Out of Equilibrium

Cells stay out of chemical equilibrium by constantly using energy and moving materials in and out. Chemical reactions in metabolism are often reversible. They can go in both directions. In one direction, they release energy to the surroundings. In the reverse direction, they absorb energy. The same idea applies to reactions that build and break down cell molecules. Proteins, for example, can be broken into individual amino acids, and amino acids can be used to build proteins again. In a closed...

oxidation and reduction of organic molecules

oxidation-and-reduction-of-organic-molecules

Electron Carriers in Cell Energy Transfer

Cell energy production depends on redox reactions, which are oxidation and reduction reactions that happen together. In oxidation, an electron is removed from an atom in a compound. In reduction, that same electron is added to another compound. Because these reactions usually occur as a pair, they are called redox reactions. When a molecule loses an electron, its potential energy goes down. The electron does not stay free in the cytoplasm. Instead, it moves to a second compound and reduces...

introduction to enzymes

Enzyme Function, Cofactors, and Inhibitors

Enzymes are proteins that speed up biochemical reactions without being used up. Humans have used enzymes since about 7000 BCE, when they fermented sugars to make alcohol without knowing the reaction was enzyme-catalyzed. The word enzyme was coined by Wilhelm Kuhne in 1877. It comes from the Greek words en, meaning “in” or “within,” and zyme, meaning “yeast.” Enzymes work through active sites, which are regions that bind substrates and help convert them into products. Many enzymes also have...

enzymes and activation energy

How Enzymes Lower Reaction Energy

Enzymes lower the energy needed for a chemical reaction to begin. That starting energy is called activation energy, or free energy of activation, and it is often written as Ea. During a reaction, bonds break and new bonds form. In glucose breakdown, for example, bonds between carbon atoms break and release energy because they are energy-storing bonds. Before a reaction can move forward, reactant molecules must reach a high-energy, unstable shape called the transition state. To get there, the...

introduction to enzyme kinetics

Graphing Enzyme Kinetics Data

Enzyme kinetics uses graphs to show how fast a biochemical reaction happens. Scientists measure the initial reaction rate, or velocity (Vo), at different substrate concentrations ([S]). They may also run trials with inhibitors or other molecules that change the reaction rate. The results are often plotted as Vo against [S]. For many single-substrate reactions, the data fits the Michaelis-Menten equation. This equation, named after Leonor Michaelis and Maud Menten, helps estimate the maximum...

turnover number and catalytic efficiency

How Fast Enzymes Work in Digestion

Enzymes can work at very different speeds, and their turnover number shows how fast they convert substrate molecules into products. Turnover number is the maximum number of substrate molecules an enzyme can transform per unit time. For most enzymes, this value is between 1 and 1000 molecules per second. Some enzymes are especially fast. Catalase has the highest known turnover number and can convert up to 2.8×10^6 molecules of hydrogen peroxide into water and oxygen each second. Lysozyme has...

catalytically perfect enzymes

Catalytically perfect enzymes are enzymes that speed up biochemical reactions at very high rates. The idea was first proposed by W. J. Albery and J. R. Knowles in 1976. These enzymes have catalytic efficiency values of about 10^8 to 10^9 M^-1 s^-1 and are also called diffusion-controlled enzymes because diffusion of the substrate into the active site is the only rate-limiting step. Examples of catalytically perfect enzymes include triose phosphate isomerase, fumarase, and superoxide dismutase.

introduction to mechanisms of enzyme catalysis

introduction-to-mechanisms-of-enzyme-catalysis

How Enzymes Change Shape to Catalyze

Enzyme catalysis depends on how enzymes bind substrates and how the active site responds during the reaction. Scientists once described this process with a simple lock-and-key model, where the enzyme and substrate fit together in one instant. Research now supports induced fit, a more dynamic model in which binding causes a small change in the enzyme’s shape. That shift helps create an ideal match between the enzyme and the substrate’s transition state, which improves catalysis. The active site...

ligand binding and linkage

Ligand Binding and Allosteric Effects

Ligand binding and linkage describe how one molecule can affect another when it binds to a protein. In this topic, the focus is on how binding at one site can influence activity at a different site on the same protein. This idea is important for understanding protein function in high school biology. It helps explain why some proteins respond more strongly after a ligand attaches. The transcript centers on the connection between ligand binding and linkage, which is a key concept in molecular...

cooperative allosteric transitions

How Proteins Shift Shape Together

Proteins can change shape in a coordinated way during allosteric transitions. In a cooperative transition, one part of the protein affects another part, so the change spreads through the molecule. These shape changes help proteins switch between different states. The shift can influence how the protein works and how it responds to other molecules. Cooperative allosteric transitions are an important idea in protein function. They explain how a small change at one site can lead to a larger...

ribozymes

Catalytic RNA: Ribozymes in Action

Ribozymes are RNA molecules that can act as enzymes. They help speed up specific chemical reactions without being protein enzymes. This makes them an important example of RNA with more than one job in the cell. Some ribozymes can cut RNA molecules, and others can join them together. This shows that RNA can do catalytic work as well as carry genetic information. Ribozymes are a key part of how scientists think about the many roles of RNA in biology. One well-known ribozyme is ribonuclease P,...

atp energy storage and release

ATP Powers Cellular Transport and Reactions

ATP powers cellular transport and many reactions by transferring energy through phosphorylation. ATP is a highly unstable molecule. If it is not used quickly, it breaks down into ADP and inorganic phosphate, and the released energy is lost as heat. Cells use ATP through energy coupling. This means the exergonic reaction of ATP hydrolysis is linked to an endergonic reaction so the reaction can move forward. One major example is the sodium-potassium pump, a transmembrane ion pump that is vital...

atp and macromolecule synthesis

ATP in Building Cell Macromolecules

ATP helps cells build biological macromolecules. These organic compounds are mainly made of carbon atoms bonded to hydrogen, oxygen, nitrogen, and small amounts of other elements. The four major classes of biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Most macromolecules start as small subunits called monomers. Cells join monomers with covalent bonds to make larger molecules called polymers. This building process needs energy, so cells depend on ATP, the...

coupled reactions

ATP Powers Cellular Work

ATP powers many kinds of cellular work by coupling energy-releasing reactions to energy-requiring ones. Some reactions happen on their own and release energy. Others need an energy input to move forward. Cells link these reactions so important processes can still occur. Adenosine triphosphate, or ATP, stores energy that cells can use quickly. ATP hydrolysis is the breaking of ATP, and it releases energy. Cells often use that released energy to drive endergonic reactions, which are reactions...

key terms and concepts

Learn how catalytically perfect enzymes work, why diffusion can limit their speed, and how examples like TPI and superoxide dismutase protect cells.

Diffusion-Controlled Enzymes and Reaction Speed | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Virginia  Standards of Learning

HIgh School

BIO.2

BIO.2.c

Chemistry

CH.7

CH.7.f

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.4

SC.912.L.18.11

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The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at ...

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For many years, scientists thought that enzyme-substrate binding took place in a simple &#34;lock-and-key&#34; fashion. This model stated that the enzyme ...

Ligand Binding and Linkage

Cooperative Allosteric Transitions

Ribozymes

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Diffusion-Controlled Enzymes and Reaction Speed

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