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

Katalytisch perfekte Enzyme haben die maximale katalytische Effizienz mit hohen Umsatzzahlen, kcat, und starken Affinitäten zu ihren Substraten, KM. 
 
Das Verhältnis von kcat zu KM misst den katalytischen Wirkungsgrad. Für katalytisch perfekte Enzyme liegt dieser Wert zwischen 108 und 109 pro molarem Substrat pro Sekunde. 
 
Substratdiffusion ist die ständige Bewegung von Substratmolekülen, die durch molekulare Bewegung verursacht wird. Substrate müssen innerhalb der Zelle diffundieren, um mit ihren Enzymen interagieren zu können. 
 
Die Reaktionsgeschwindigkeiten katalytisch perfekter Enzyme werden nur durch die Geschwindigkeit der Substratdiffusion in das aktive Zentrum oder die Produktfreisetzung aus dem aktiven Zentrum begrenzt. Einige Enzyme haben katalytische Perfektion durch elektrostatische Kräfte erreicht, die Substrate anziehen und in ihr aktives Zentrum leiten. 
 
In katalytisch perfekten Enzymen entsteht bei jeder Enzym-Substrat-Kollision ein Zwischenprodukt, das sich schnell in Produkte umwandelt.

<ol>
	<li>Ahern, K., & Rajagopal, I. (2021, 6. März). Perfekte Enzyme. Staatliche Universität von Oregon. https://bio.libretexts.org/@go/page/3036.</li>
	<li>Petterson, G. (1992). Evolutionäre Optimierung der katalytischen Effizienz von Enzymen. Europäische Zeitschrift für Biochemie, 206(1), 289-295.</li>
	<li>Bar-Even, A., Milo, R., Noor, E., & Tawfik, D. S. (2015). Das mäßig effiziente Enzym: vergebliche Begegnungen und Enzymschlappheit. Biochemie, 54(32), 4969-4977.</li>
</ol>

katalytisch perfekte enzyme

Die Theorie der katalytisch perfekten Enzyme wurde erstmals 1976 von W.J. Albery und J.R. Knowles vorgeschlagen. Diese Enzyme katalysieren biochemische Reaktionen mit hoher Geschwindigkeit. Ihre katalytischen Effizienzwerte liegen zwischen 108 und 109 M-1s-1. Diese Enzyme werden auch „diffusionskontrolliert“ genannt, da der einzige geschwindigkeitsbestimmende Schritt in der Katalyse die Diffusion des Substrats in das aktive Zentrum ist. Beispiele hierfür sind Triosephosphatisomerase, Fumarase und Superoxiddismutase.

Die meisten Enzyme erreichen katalytische Perfektion aufgrund der geladenen Gruppen auf ihrer Oberfläche, die das Substrat ausrichten und in das aktive Zentrum lenken. Einige andere Enzyme haben eine spezifische Anordnung der aktiven Zentren, die zur katalytischen Perfektion beiträgt. In Enzymen wie Superoxiddismutase beschleunigen Metallionen wie Kupfer und Zink im aktiven Zentrum und geladene Aminosäuren wie Arginin in der Nähe des aktiven Zentrums die Umwandlung von Superoxidanionen in Sauerstoff und Wasserstoffperoxid. Zufällige Mutationen in Enzymen begünstigen solche Wechselwirkungen mit ihren Substraten, und Enzyme mit höherer Effizienz werden im Laufe der Zeit auf natürliche Weise ausgewählt.

Perfekte Enzyme katalysieren nicht nur hocheffiziente Reaktionen, sondern können auch dazu beitragen, Zellen vor schädlichen Reaktionszwischenprodukten zu schützen. Beispielsweise ist Triosephosphat-Isomerase (TPI) ein Enzym im glykolytischen Weg, das die gegenseitige Umwandlung von Dihydroxyacetonphosphat (DHAP) und Glycerinaldehyd-3-phosphat (G3P) katalysiert. Durch die langsame Umwandlung von DHAP in G3P entsteht ein Endiol-Zwischenprodukt, das schließlich in eine toxische Verbindung zerfällt. Da TPI ein katalytisch perfektes Enzym ist, beschleunigt es die Reaktion und wandelt das Zwischenprodukt schnell in das Produkt um, wodurch unerwünschte Verbindungen vermieden werden. Bisher haben sich nur sehr wenige Enzyme entwickelt, die katalytisch perfekt sind. Die meisten Enzyme sind mäßig effizient.

Katalytisch perfekte Enzyme

Die Theorie der katalytisch perfekten Enzyme wurde erstmals 1976 von W.J. Albery und J. R. Knowles vorgeschlagen. Diese Enzyme katalysieren biochemische Reaktionen bei ...

Education

Lehre

JoVE Core

Cell Biology

Zellbiologie

Unit 1

Einheit 1

Energy and Catalysis

Energie und Katalyse

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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

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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

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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

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non-equilibrium in the cell

Cells Stay Out of Equilibrium

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oxidation and reduction of organic molecules

oxidation-and-reduction-of-organic-molecules

Electron Carriers in Cell Energy Transfer

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enzymes and activation energy

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Graphing Enzyme Kinetics Data

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turnover number and catalytic efficiency

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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...

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ribozymes

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atp energy storage and release

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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

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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 Zellbiologie veranschaulicht komplexe zelluläre Prozesse in leicht verständlichen und dennoch umfassenden animierten Videolektionen. Diese Sammlung konzentriert sich auf die wesentlichen Bestandteile und Funktionen von Zellen, einschließlich Organellen und Membranen, Zelltransport und Zellenergie. Ergänzt wird sie durch Videos von Wissenschaftlern in Aktion, die die Anwendung der Zellbiologie in realen Forschungsexperimenten demonstrieren.

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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Nucleic Acids and Nucleotides

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Nucleic Acid Structure

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LS.Bio.1.1

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The use of enzymes by humans dates to 7000 BCE. Humans first used enzymes to ferment sugars and produce alcohol without knowing that this was an ...

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The activation energy (or free energy of activation), abbreviated as Ea, is the small amount of energy input necessary for all chemical reactions to ...

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Enzyme kinetics studies the rates of biochemical reactions. Scientists monitor the reaction rates for a particular enzymatic reaction at various substrate ...

Turnover Number and Catalytic Efficiency

The turnover number of an enzyme is the maximum number of substrate molecules it can transform per unit time. Turnover numbers for most enzymes range from ...

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 ...

Introduction to Mechanisms of Enzyme Catalysis

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

Carry out investigations to illustrate how enzymes act as catalysts for biochemical reactions and how environmental factors affect enzyme activity.

What are Cells?

Cells are the smallest and basic units of life, whether it is a single cell that forms the entire organism, e.g., in a bacterium or trillions of them, ...

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Prokaryotic Cells

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Cytoplasm

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The Nucleus

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Endoplasmic Reticulum

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Lysosomes

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Overview of Myosin Structure and Function

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LS.Bio.1.3

Analyze how the relationship between structure and function supports life processes within organisms.

Diffusion-Controlled Enzymes and Reaction Speed

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