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

Katalitycznie doskonałe enzymy mają maksymalną wydajność katalityczną z wysokimi liczbami obrotu, kcat i silnym powinowactwem do ich substratów, KM. 
 
Stosunek kcat do KM mierzy sprawność katalityczną. W przypadku enzymów doskonałych katalitycznie wartość ta waha się od 108 do 109 na substrat molowy na sekundę. 
 
Dyfuzja substratu to ciągły ruch cząsteczek substratu spowodowany ruchem molekularnym. Substraty muszą dyfundować w komórce, aby wchodzić w interakcje z ich enzymami. 
 
Szybkość reakcji katalitycznie doskonałych enzymów jest ograniczona jedynie prędkością dyfuzji substratu do miejsca aktywnego lub uwalniania produktu z miejsca aktywnego. Niektóre enzymy osiągnęły katalityczną doskonałość dzięki siłom elektrostatycznym, które przyciągają i kierują substraty do ich miejsca aktywnego. 
 
W katalitycznie doskonałych enzymach każde zderzenie enzymu z substratem daje półprodukt, który szybko przekształca się w produkty.

<ol>
	<li>Ahern, K. i Rajagopal, I. (2021, 6 marca). Doskonałe enzymy. Uniwersytet Stanowy Oregonu. https://bio.libretexts.org/@go/page/3036.</li>
	<li>Petterson, G. (1992). Ewolucyjna optymalizacja wydajności katalitycznej enzymów. Europejski Dziennik Biochemii, 206(1), 289-295.</li>
	<li>Bar-Even, A., Milo, R., Noor, E. i Tawfik, D. S. (2015). Umiarkowanie wydajny enzym: daremne spotkania i wiotkość enzymów. Biochemia, 54(32), 4969-4977.</li>
</ol>

katalitycznie doskonałe enzymy

Teorię katalitycznie doskonałych enzymów po raz pierwszy zaproponowali W.J. Albery i J.R. Knowles w 1976 roku. Enzymy te katalizują reakcje biochemiczne z dużą szybkością. Ich skuteczność katalityczna waha się w granicach 108-109 M-1s-1. Enzymy te nazywane są także „kontrolowanymi dyfuzyjnie”, ponieważ jedynym etapem ograniczającym szybkość katalizy jest dyfuzja substratu do miejsca aktywnego. Przykłady obejmują izomerazę triozofosforanową, fumarazę i dysmutazę ponadtlenkową. Większość enzymów osiąga doskonałość katalityczną dzięki obecności na ich powierzchni naładowanych grup, które orientują i kierują substrat do miejsca aktywnego. Niektóre inne enzymy mają specyficzny układ miejsc aktywnych, przyczyniając się do doskonałości katalitycznej. W enzymach, takich jak dysmutaza ponadtlenkowa, jony metali, takich jak miedź i cynk, w miejscu aktywnym i naładowane aminokwasy, takie jak arginina, w pobliżu miejsca aktywnego, przyspieszają konwersję anionu ponadtlenkowego w tlen i nadtlenek wodoru. Losowe mutacje w enzymach sprzyjają takim interakcjom z ich substratami, a enzymy o wyższej wydajności są naturalnie wybierane z biegiem czasu.   Doskonałe enzymy nie tylko katalizują wysoce wydajne reakcje, ale mogą także pomóc chronić komórki przed szkodliwymi półproduktami reakcji. Na przykład izomeraza fosforanu triozy (TPI) jest enzymem na szlaku glikolitycznym, który katalizuje wzajemną konwersję fosforanu dihydroksyacetonu (DHAP) i 3-fosforanu aldehydu glicerynowego (G3P). Powolna konwersja DHAP do G3P tworzy półprodukt enediolu, który ostatecznie rozkłada się do toksycznego związku. Ponieważ TPI jest enzymem doskonałym katalitycznie, przyspiesza reakcję i szybko przekształca półprodukt w produkt, unikając niepożądanych związków. Jak dotąd bardzo niewiele enzymów ewoluowało, aby były katalitycznie doskonałe. Większość enzymów jest umiarkowanie wydajna.

Katalitycznie doskonałe enzymy

Teoria katalitycznych enzymów doskonałych została po raz pierwszy zaproponowana przez W.J. Albery'ego i J.R. Knowlesa w 1976 roku. Enzymy te katalizują reakcje biochemiczne w ...

Education

JoVE Core

Cell Biology

Biologia komórki

Unit 1

Jednostka 1

Energy and Catalysis

Energia i kataliza

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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

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the second law of thermodynamics

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

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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.

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introduction-to-mechanisms-of-enzyme-catalysis

How Enzymes Change Shape to Catalyze

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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

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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 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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Diffusion-Controlled Enzymes and Reaction Speed

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