Name: enzyme helpers: metals and vitamins
Uploaded: 2023-04-30T10:35:36.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Life Science

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

From Molecules to Organisms: Structures and Processes

HS-LS1-1

Cofactors and Coenzymes

Alcuni enzimi si associano a molecole non proteiche o cofattori per migliorare la loro attività catalitica.
Il complesso enzima-cofattore chimicamente attivo è chiamato oloenzima e l'enzima da solo è chiamato apoenzima.
I cofattori possono essere presenti come ioni metallici inorganici come lo ione zinco nell'anidrasi carbonica o come molecole organiche chiamate coenzimi come NAD+, coenzima A e altri.
Alcuni cofattori, chiamati gruppi protesici, sono legati covalentemente agli apoenzimi. Ad esempio, nell'emoglobina, il gruppo eme, una porfirina con uno ione ferro centrale, è associato alle catene proteiche attraverso il legame covalente, il legame idrogeno e le estese interazioni idrofobiche.
Al contrario, i cofattori che sono legati transitoriamente agli enzimi agiscono come cosubstrati.
Ad esempio, il NAD+, un coenzima per l'alcol deidrogenasi, aiuta a ossidare l'alcol ad aldeide e viene ridotto a NADH. Il NADH si dissocia una volta completata la reazione e viene riossidato a NAD+ per il ciclo di reazione successivo.

<ol>
	<li>Donald Voet e Judith G Voet Biochimica. 4a ed. JOHN WILEY & SONS, INC. 2011. Pagine 473-474</li>
	<li>Nelson e Cox, Lehninger, Principi di biochimica, 7a ed. W.H. Freeman and Company, 2016. Pagine 513</li>
</ol>

cofattori e coenzimi

Gli enzimi sono proteine costituite da aminoacidi. Il gruppo funzionale di ciascun amminoacido costituente catalizza un'ampia varietà di reazioni chimiche tramite interazioni ioniche o reazioni acido-base. Tuttavia, gli amminoacidi non possono catalizzare le reazioni di ossidoriduzione e di trasferimento di gruppo e devono essere aiutati da componenti non proteici chiamati cofattori. I cofattori vengono anche definiti denti chimici di un enzima.

I cofattori possono essere ioni metallici o molecole organiche chiamate coenzimi. Questi tipi di molecole helper possono legarsi covalentemente a un enzima come gruppi prostetici o transitoriamente come co-substrati.

I cofattori sono presenti in circa il 30% delle proteine mature. Sono spesso incorporati in un enzima mentre viene ripiegato e coinvolto nella sua attività catalitica. Il magnesio è un cofattore essenziale per oltre 300 enzimi nel corpo umano, inclusa la DNA polimerasi. In questo caso, lo ione magnesio aiuta a formare il legame fosfodiestere sulla struttura portante del DNA. Ferro, rame, cobalto e manganese sono altri cofattori comuni.

Molte vitamine sono coenzimi, come la biotina della famiglia delle vitamine B. È essenziale in vari enzimi che trasferiscono l'anidride carbonica da una molecola all'altra. Oltre alla biotina, il NAD+, un derivato della vitamina B3 e il retinolo o vitamina A, sono altri esempi di cofattori essenziali per il nostro organismo e devono essere ingeriti con la dieta poiché non possono essere prodotti dalle cellule umane.

Cofattori e Coenzimi

Gli enzimi sono proteine costituite da amminoacidi. Il gruppo funzionale di ciascun amminoacido costituente catalizza un'ampia varietà di reazioni chimiche ...

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Protein Function

Funzione proteica

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

enzyme helpers: metals and vitamins

Enzyme helpers include cofactors and coenzymes. Enzymes are proteins made of amino acids, and the functional groups on those amino acids can drive many chemical reactions through ionic interactions or acid-base reactions. But amino acids alone cannot handle oxidation-reduction and group transfer reactions, so they need non-protein helpers called cofactors.

Cofactors are often described as the chemical teeth of an enzyme. They can be metal ions or organic molecules called coenzymes. These helper molecules may bind tightly as prosthetic groups, or they may bind only for a short time as co-substrates.

Cofactors are present in about 30% of mature proteins. They are often added as an enzyme folds and becomes active in catalysis. Magnesium is an important cofactor for more than 300 enzymes in the human body, including DNA polymerase. In that enzyme, magnesium helps form the phosphodiester bond in the DNA backbone.

Other common cofactors include iron, copper, cobalt, and manganese. Many vitamins also act as coenzymes, including biotin from the vitamin B family. Biotin helps enzymes transfer carbon dioxide from one molecule to another.

Some cofactors must come from the diet because human cells cannot make them. Examples include biotin, NAD+ from vitamin B3, and retinol, or vitamin A. These molecules are essential for normal body function.

Enzyme Helpers: Metals and Vitamins

ligand binding sites

Ligand Binding Sites in Proteins

Ligand binding sites are specific parts of a protein where a ligand can attach. A ligand is a molecule that binds to another molecule, often to help start or change a biological process. These sites matter because the shape and chemistry of the protein help determine which ligands can fit and bind. Proteins do not bind every ligand in the same way. The binding site provides a matching surface that supports a close interaction. In many cases, this interaction is important for how cells respond...

protein-protein interfaces

Protein Binding Surfaces and Contacts

Protein binding surfaces and contacts help proteins recognize and attach to each other. These interfaces are the regions where two proteins meet and interact. They are important for many cell processes and for how proteins work together. A protein-protein interface is not just a random touch point. It is shaped by the three-dimensional form of each protein. The matching surfaces allow a stable interaction to form when the proteins fit together well. Studying these interfaces helps explain how...

conserved binding sites

Conserved Binding Sites in Protein Families

Conserved binding sites are regions on proteins that stay similar across related proteins. These shared areas often help proteins interact with the same molecules. For this reason, they are useful clues when comparing protein families. A conserved site can help identify where a protein binds. It can also show which parts of the protein are important for function. When the same pattern appears in several proteins, it suggests that the site has been kept through evolution. Scientists look at...

cofactors and coenzymes

Enzyme helpers include cofactors and coenzymes. Enzymes are proteins made of amino acids, and the functional groups on those amino acids can drive many chemical reactions through ionic interactions or acid-base reactions. But amino acids alone cannot handle oxidation-reduction and group transfer reactions, so they need non-protein helpers called cofactors. Cofactors are often described as the chemical teeth of an enzyme. They can be metal ions or organic molecules called coenzymes. These...

cooperative allosteric transitions

Allosteric Changes in Protein Shape

Allosteric changes in protein shape help explain how some proteins switch between active and inactive states. These transitions are cooperative, which means a change in one part of the protein can affect other parts of the same molecule. The video focuses on how these shifts in shape support protein function. It also shows that allosteric transitions can be described with different models. In the concerted model, the protein changes shape as a whole. In the sequential model, the change happens...

protein kinases and phosphatases

Protein Kinases and Phosphatases in Cell Control

Protein kinases and phosphatases help control how proteins work in cells. Kinases add phosphate groups to proteins. Phosphatases remove those phosphate groups. This phosphorylation and dephosphorylation process can change a protein’s shape and activity. It is one way cells turn protein function on or off at the right time. These changes also help cells respond to signals and manage many cell activities. Together, protein kinases and phosphatases keep cellular signaling balanced. When one adds...

gtpases and their regulation

GTPase Molecular Switches and Control

GTPases are molecular switches that help control cell activity. They bind guanosine triphosphate, or GTP, and can change between active and inactive states. This switch-like behavior makes them important in many cell processes. The protein is active when GTP is bound and inactive when guanosine diphosphate, or GDP, is bound. GTPases can also turn themselves off by breaking down GTP into GDP. This built-in control helps cells regulate when the protein is on or off. Their activity is regulated...

covalently linked protein regulators

Protein Regulation by Covalent Bonds

Protein regulation by covalent bonds helps control how cells respond to changing conditions. A covalent bond is a strong chemical link, and in this context it can change how a protein behaves. Some regulators work by attaching a chemical group directly to a protein. This covalent change can alter the protein's activity, its location in the cell, or how long it stays active. Because the change is built into the protein itself, it can have a strong effect on cell function. Covalently linked...

protein complexes with interchangeable parts

protein-complexes-with-interchangeable-parts

Modular Protein Complexes in Cells

Protein complexes in cells can be built from interchangeable parts. This modular design lets some complexes share common subunits while still changing their behavior. A well-known example is the ubiquitin ligase complex called SCF. SCF stands for Skp1-Cullin-F-box, and it helps attach ubiquitin, a small protein tag, to target proteins. The core of SCF stays the same, but the F-box protein can change. The interchangeable F-box subunit gives the complex its specificity. Different F-box proteins...

mechanical protein function

Proteins That Generate Cell Movement

Mechanical proteins help cells and tissues move. They turn chemical energy into force and motion. This process is important in many biological systems. These proteins are also called motor proteins. They interact with cell structures and can produce directed movement. In muscle cells, they support contraction. In other cells, they help with transport and shape changes. Mechanical protein function is a key part of how living systems work. It links protein activity to movement at the cellular...

structural protein function

Structural Proteins in Cells and Tissues

Structural proteins help cells and tissues keep their shape and strength. They are an important part of living systems because they provide support where it is needed most. Many structural proteins form fibers or other sturdy forms that resist stretching and wear. These proteins work as building materials in the body and help keep structures stable over time. Examples of structural proteins include collagen, actin, myosin, and keratin. Each one supports a different part of the body, but all...

protein networks

Mapping Protein Interaction Networks

Protein interaction networks show how proteins work together inside a cell. These networks help scientists see which proteins connect with each other and how those links support cell activity. Researchers often use online tools to build and study these networks. The transcript points to IntAct and STRING as examples of resources that can help predict and organize protein interactions. These tools make it easier to compare protein links and look for patterns in the network. Protein networks...

key terms and concepts

Learn how cofactors and coenzymes help enzymes work, from metal ions like magnesium to vitamin-based helpers such as biotin and NAD+.

Enzyme Helpers: Metals and Vitamins | 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.

Florida Department of Education

SC.912.L.18

SC.912.L.18.4

Characteristics of Life

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Protein and Protein Structures

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Proteins: From Genes to Degradation

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Conserved Binding Sites

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GTPases and their Regulation

Covalently Linked Protein Regulators

Protein Complexes with Interchangeable Parts

Mechanical Protein Function

Structural Protein Function

Protein Networks

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.]

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structural-organization-of-the-human-body-an-overview

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The Parasympathetic Nervous System

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The Sympathetic Nervous System

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an-introduction-to-the-zebrafish-danio-rerio

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Homeostasis
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Blood Withdrawal II

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Within the skeletal system, the structure of a bone, or osseous tissue, can be exemplified in a long bone, like the femur, where there are two types of ...

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

HS-LS1-2

What is Homeostasis?

Maintaining homeostasis requires that the body continuously maintain its internal conditions. Each physiological condition has a particular set point, ...

Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. [Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.] [Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

HS-LS1-3

Enzyme Helpers: Metals and Vitamins

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