Name: enzyme action and inhibition
Uploaded: 2020-09-24T15:06:50.000Z
Duration: 2 min 34 s
Channel: JoVE

K12 Standards

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

NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.5.1

Enzymes

Las enzimas son catalizadores biológicos que aceleran la velocidad de las reacciones bioquímicas. La mayoría de las enzimas son proteínas, compuestas por aminoácidos;mientras que algunas son moléculas de ácido ribonucleico conocidas como ribozimas. Las enzimas actúan reduciendo la energía de activación de una reacción, aumentando así la velocidad de reacción.Pueden catalizar tanto la síntesis como la ruptura de los enlaces químicos, pero no afectan la dirección o el equilibrio de la reacción. Cada enzima se une a un reactivo específico, llamado sustrato, y cataliza una reacción particular. El sustrato se une a una región catalítica distinta de la enzima llamada sitio activo a través de interacciones como fuerzas intermoleculares y enlaces covalentes transitorios, lo que da como resultado un complejo enzima-sustrato.Esta unión es muy específica debido a la complementariedad conformacional requerida entre la enzima y su sustrato. Por lo tanto, una enzima en particular solo puede catalizar reacciones específicas en función de su conformación. Una forma sencilla de entender la formación de complejos es el modelo de cerradura y llave, que plantea la hipótesis de que el sustrato encaja en el sitio activo de la enzima de forma análoga a una llave"que encaja en su cerradura"correspondiente.Sin embargo, otro modelo, el modelo de ajuste inducido, tiene en cuenta la naturaleza dinámica del complejo. Este modelo establece que cuando un sustrato se une induce pequeños cambios conformacionales, lo que resulta en un ajuste más estrecho que favorece la reacción. La energía de activación de una reacción se puede reducir mediante varios métodos.Los mecanismos comunes incluyen inducir cambios conformacionales en el sustrato que permiten que un enlace se rompa más fácilmente o acercar los grupos reactivos de dos sustratos promoviendo así la formación de enlaces. La actividad enzimática puede ser suprimida temporal o permanentemente por moléculas naturales o sintéticas llamadas inhibidores. Por ejemplo, un inhibidor competitivo compite con el sustrato para unirse al sitio activo de la enzima, evitando así la unión del sustrato.Por otro lado, un inhibidor no competitivo se une a otra ubicación de la enzima, lo que provoca un cambio conformacional en el sitio activo, reduciendo la actividad catalítica de la enzima.

enzimas

Dentro de los organismos vivos, las enzimas actúan como catalizadores de muchas reacciones bioquímicas involucradas en el metabolismo celular. El papel de las enzimas es reducir las energías de activación de las reacciones bioquímicas formando complejos con sus sustratos. La disminución de las energías de activación favorece un aumento en las velocidades de las reacciones bioquímicas.
 Las deficiencias enzimáticas a menudo pueden traducirse en enfermedades que ponen en peligro la vida. Por ejemplo, una anomalía genética que resulta en la deficiencia de la enzima G6PD (glucosa-6-fosfato deshidrogenasa) afecta negativamente la vía metabólica que suministra NADPH a las células.
 Una interrupción en esta vía metabólica puede reducir el glutatión en los glóbulos rojos causando daño a otras enzimas y proteínas como la hemoglobina. La metabolización excesiva de la hemoglobina aumenta el nivel de bilirrubina, lo que lleva a la ictericia, una afección que puede volverse grave. Por lo tanto, las personas que sufren de deficiencia de G6PD deben evitar ciertos alimentos y medicamentos que contienen productos químicos que podrían desencadenar daños a sus glóbulos rojos deficientes en glutatión.
 Función y estructura enzimática 
 Las enzimas se agrupan en diferentes clases basándose en la función específica que realizan. Por ejemplo, las oxidoreductasas están involucradas en reacciones redox, mientras que las transferasas catalizan la transferencia de grupos funcionales. La formación de enlaces con hidrólisis de ATP requiere ligasas, mientras que las reacciones de hidrólisis y la formación de enlaces dobles son catalizadas por hidrolasas y ligasas, respectivamente. Las enzimas de isomerasa generalmente catalizan reacciones de isomerización. 
 Las enzimas generalmente poseen sitios activos. Estas son regiones específicas en la molécula con una conformación que favorece la unión de la enzima con un sustrato específico (una molécula reactante) para formar un complejo enzima-sustrato o el intermediario de la reacción.
 Dos modelos—el modelo de llave y cerradura y el modelo de ajuste inducido—intentan explicar el funcionamiento de un sitio activo (Figura 1). La hipótesis más simplista de llave y cerradura sugiere que el sitio activo y la forma molecular del sustrato son complementarios, ajustándose como una llave en una cerradura (Figura 1a). Por otro lado, la hipótesis de ajuste inducido sugiere que la molécula enzimática es flexible y cambia de forma para adaptarse a la unión con el sustrato (Figura 1b).
 Sin embargo, tanto el modelo de llave y cerradura como el modelo de ajuste inducido explican el hecho de que las enzimas sólo pueden unirse con sustratos específicos y catalizar sólo una reacción en particular.
 <img alt="Eq1" src="/files/ftp_upload/11384/11384_Image_1.png" style="text-align: center; height: 300px;" />
 Figura 1 (a) Según el modelo de llave y cerradura, la forma del sitio activo de una enzima se ajuste perfectamente al sustrato. (b) De acuerdo con el modelo de ajuste inducido, el sitio activo es algo flexible, y puede cambiar de forma para unirse con el sustrato.
 Inhibidores enzimáticos
 La actividad de las enzimas también puede ser interrumpida por el proceso de inhibición enzimática. Existen varios tipos comunes de inhibición enzimática.
 Durante la inhibición competitiva, una molécula (natural o sintética) que no sea el sustrato se une directamente al sitio activo de la enzima. La similitud estructural y química del inhibidor con el sustrato facilita su unión al sitio activo. Tales inhibidores competitivos, por lo tanto, compiten con los sustratos, evitando que se vinculen a la enzima. Con más frecuencia, el aumento de la concentración de sustrato puede suprimir los efectos de la inhibición competitiva.
 En la inhibición no competitiva, una molécula (natural o sintética) se une a una región alostérica (otra) de la enzima, diferente de su sitio activo. La unión a los inhibidores causa un cambio conformacional en el sitio activo de la enzima, resultando en una disminución en la capacidad de la enzima para catalizar la reacción. A diferencia de la inhibición competitiva, un aumento en la concentración de sustrato no mitiga los efectos inhibitorios de la inhibición no competitiva.
 Parte de este texto está adaptado de<a href="https://openstax.org/books/chemistry-2e/pages/12-7-catalysis"> Openstax, Química 2e, Sección 12.7: Catálisis.</a>

Enzimas

Dentro de los organismos vivos, las enzimas actúan como catalizadores de muchas reacciones bioquímicas involucradas en el metabolismo celular. El papel de las enzimas es reducir el ...

Education

Educación

JoVE Core

Química

Chemical Kinetics

Cinética Química

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

enzyme action and inhibition

Enzymes are biological catalysts that speed up many reactions in living organisms. They help control cellular metabolism by lowering the activation energy needed for biochemical reactions. When activation energy drops, reaction rates can increase.

Enzyme problems can also lead to serious disease. A genetic abnormality that causes G6PD, or glucose-6-phosphate dehydrogenase, deficiency can disrupt the pathway that supplies NADPH to cells. In red blood cells, this can reduce glutathione and damage other enzymes and proteins such as hemoglobin. As hemoglobin is broken down too much, bilirubin builds up and can cause jaundice. People with G6PD deficiency often need to avoid certain foods and medicines that may trigger damage to their red blood cells.

Enzymes are grouped by the reactions they carry out. Oxidoreductases take part in redox reactions. Transferases move functional groups from one molecule to another. Ligases form bonds and use ATP hydrolysis, while hydrolases drive hydrolysis reactions and lyases help form double bonds. Isomerases catalyze isomerization reactions.

Most enzymes have an active site, which is the region that binds a specific substrate, or reactant molecule. The enzyme and substrate form an enzyme-substrate complex, which acts as the reaction intermediate. Two models explain how this binding works. In the lock-and-key model, the active site and substrate fit together like a key in a lock. In the induced-fit model, the enzyme changes shape to fit the substrate. Both models explain enzyme specificity, meaning an enzyme usually binds only certain substrates and catalyzes only one particular reaction.

Enzyme activity can also be blocked by inhibitors. In competitive inhibition, an inhibitor that is similar to the substrate binds directly to the active site and competes with the substrate. Increasing substrate concentration can often reduce this effect. In non-competitive inhibition, the inhibitor binds to an allosteric site, which is a different region of the enzyme. This binding changes the shape of the active site and lowers enzyme activity. Unlike competitive inhibition, adding more substrate does not fix non-competitive inhibition.

Enzyme Action and Inhibition

reaction rate

Measuring Reaction Rates

Measuring reaction rates shows how fast reactants are used up or products are formed over time. The rate of reaction is the change in the amount of a reactant or product per unit time. Because of that, scientists measure how a property changes as the reaction proceeds and connect that change to reactant or product amounts. For reactions that make or use a gas, the rate can be followed by changes in volume or pressure. A rate expression is the mathematical way to write how concentration changes...

measuring reaction rates

Tracking Reaction Kinetics with Light and Pressure

Reaction kinetics can be tracked with polarimetry, spectrometry, and pressure measurements. These methods let scientists follow a reaction without disturbing the sample. They also help determine how reactant or product concentrations change over time. Polarimetry is used for optically active substances. These substances rotate the plane of polarized light, which is called optical rotation. The effect comes from molecular structure. Normal monochromatic light is unpolarized, but after it passes...

concentration and rate law

Reaction Order from Concentration

Reaction order from concentration shows how reactant amounts affect reaction rate. Rate laws, also called differential rate laws or rate equations, are mathematical expressions that connect reaction rate with the concentrations of reactants. For a generic reaction a A + b B → products, the rate law can be written using the reactant concentrations [A] and [B] and a rate constant k. In a rate law, k is the rate constant for one specific reaction at one specific temperature. The exponents m and n...

determining order of reaction

Finding Rate Law from Initial Rates

Rate laws connect the speed of a chemical reaction to the concentration of its reactants. The rate constant, k, and the reaction orders are not taken from the chemical equation. They are found experimentally by watching how the rate changes when the reactant concentrations change. One common way to do this is the method of initial rates. In this method, several trials are run with different starting concentrations. The measured rates are then compared to determine the reaction orders and,...

the integrated rate law: the dependence of concentration on time

the-integrated-rate-law-the-dependence-of-concentration-on-time

Reading Reaction Progress with Integrated Laws

Integrated rate laws connect reaction concentration to time. They help show how much reactant or product is present after a certain period. They can also help estimate how long a reaction must run to reach a given extent. A common use is finding how long radioactive material must be stored before its radioactivity drops to a safe level. These equations come from the differential rate law after it is integrated with respect to time. For a first-order reaction, where rate = k[A], the integrated...

half-life of a reaction

Reaction Half-Life in Kinetics

Reaction half-life is the time needed for half of a reactant to be consumed. After each half-life, half of the remaining reactant is used up. A hydrogen peroxide decomposition example shows this pattern clearly. The concentration drops from 1.000 M to 0.500 M in the first 6.00 hours, then to 0.250 M in the next 6.00 hours, and then to 0.125 M in the third period. Each later 6.00-hour interval removes half of what is left. For first-order reactions, the half-life does not depend on the reactant...

temperature dependence on reaction rate

Collision Theory and Reaction Speed

Collision theory explains why reaction speed depends on how particles collide. Atoms, molecules, or ions must come close together before they can react. The theory says the reaction rate depends on the collision rate, the orientation of the colliding species, and whether the collision has enough energy for bonds to change. A gas-phase reaction between carbon monoxide and oxygen shows why orientation matters. The molecules can collide in more than one way. If the oxygen side of carbon monoxide...

arrhenius plots

Determining Activation Energy from Temperature

The Arrhenius equation links activation energy and the rate constant, k, for chemical reactions. It is written as k = Ae−Ea/RT. In this equation, R is the ideal gas constant with a value of 8.314 J/mol·K, T is the temperature on the kelvin scale, Ea is the activation energy in J/mole, e is the constant 2.7183, and A is the frequency factor. The frequency factor depends on collision frequency and the orientation of reacting molecules. Experimental kinetic data can be used to find the activation...

reaction mechanisms

Elementary Steps in Reaction Mechanisms

Chemical reactions can happen in steps, and a balanced equation does not show the full path at the molecular level. A reaction mechanism, also called a reaction path, gives the step-by-step process that explains how reactants become products. The decomposition of ozone is one example of a reaction that can be described by a sequence of steps. Each step in a mechanism is an elementary reaction. These elementary reactions happen in order, and when they are added together, they give the balanced...

rate-determining steps

Reaction Bottlenecks in Chemical Kinetics

Reaction bottlenecks help explain rate-determining steps in multistep reaction mechanisms. In a mechanism with several elementary steps, one step is often much slower than the others. That slowest step is called the rate-limiting step, or rate-determining step. A reaction cannot move faster than its slowest step, so this step controls the overall reaction rate. The idea is like traffic on a four-lane freeway with one lane closed. Cars can only move as fast as the bottleneck allows. In the same...

catalysis

Catalyst Action in Reaction Rates

Catalysts change the rate of a chemical reaction by giving it a faster path. A catalyst increases reaction rate without being consumed during the process. Its effect is often explained with reaction mechanisms and energy diagrams. For an endothermic reaction, the reactants and products start and end at the same energies in both cases. The uncatalyzed path is a one-step mechanism with one transition state. The catalyzed path follows a different mechanism with two transition states and a lower...

enzymes

Enzymes are biological catalysts that speed up many reactions in living organisms. They help control cellular metabolism by lowering the activation energy needed for biochemical reactions. When activation energy drops, reaction rates can increase. Enzyme problems can also lead to serious disease. A genetic abnormality that causes G6PD, or glucose-6-phosphate dehydrogenase, deficiency can disrupt the pathway that supplies NADPH to cells. In red blood cells, this can reduce glutathione and...

key terms and concepts

Explore how enzymes speed reactions, how active sites work, and how competitive and non-competitive inhibitors affect enzyme activity in high school biology.

Enzyme Action and Inhibition | JoVE K12

chemistry

JoVE Core Química da vida a los conceptos de química general mediante lecciones de vídeo basadas en animaciones, concisas y fáciles de entender. Además, en los vídeos de científicos en acción, se muestran experimentos de investigación clásicos y originales realizados en laboratorios de todo el mundo.

Pennsylvania State Academic Standards

Physical Science

Chemical Reactions

3.2.9-12.D

3.2.9-12.E

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Chemical reactions

Virginia  Standards of Learning

HIgh School

CH.7

CH.7.f

Arizona Science Standards

High School

HS.P1

HS.P1U1.3

Next Generation Science Standards

Matter and Its Interactions

HS-PS1-4

HS-PS1-5

Florida Department of Education

SC.912.P.12

SC.912.P.12.12

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PS.Chm.3.1

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PS.Chm.3.2

Analyze the structure of atoms and isotopes.

Enzyme Action and Inhibition

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