Lysozyme
TLDRThe video script narrates the discovery of lysozyme, an antibacterial enzyme, by Alexander Fleming, which eventually led to the discovery of penicillin. Lysozyme is a crucial part of the body's immune system, found in fluids like tears, saliva, and mucus, providing a first line of defense against bacteria. It functions by hydrolyzing the bacterial cell wall, specifically targeting the peptidoglycan strands. The enzyme's active site, with the help of two key amino acids, glutamate 35 and aspartate 52, breaks the glycosidic bond, weakening the cell wall and causing bacterial death. Lysozyme is particularly effective against gram-positive bacteria and is abundant in breast milk and egg whites for protection. Despite its importance, it is just one component of the complex immune system.
Takeaways
- 🔍 Alexander Fleming discovered lysozyme when a culture sample was accidentally contaminated with a patient's mucus, which killed bacteria.
- 🛡️ Lysozyme is a part of the body's immune system and acts as a first line of defense against bacteria by hydrolyzing their cell walls.
- 💧 As a hydrolytic agent, lysozyme consumes water to break chemical bonds, specifically the glycosidic linkages of bacterial cell walls.
- 🧬 Lysozyme has a two-domain structure composed of alpha helixes and beta strands, which allows it to bind specifically to bacterial peptidoglycan strands.
- 🔬 The enzyme's active site targets the peptidoglycan strands, where two key amino acids, glutamate 35 and aspartate 52, play a crucial role in breaking the glycosidic bond.
- ⚔️ The mechanism of lysozyme involves an electrophile (glutamate) donating a proton, enabling aspartate to act as a nucleophile and attack the glycosidic bond.
- 🌀 The conformational change induced by lysozyme's action on peptidoglycan is critical for its efficiency as an enzyme.
- 💥 Breaking the glycosidic bond weakens the bacterial cell wall, leading to osmotic lysis and death of the bacteria.
- 🌊 Lysozyme is important for the immune system and is found in bodily fluids like tears, saliva, and mucus, as well as in high concentrations in breast milk and egg white.
- 🚫 While lysozyme is effective against gram-positive bacteria with peptidoglycan cell walls, it is less effective against other types of bacterial cell walls.
- 👶 Lysozyme is particularly vital for newborns, as low levels can increase the risk of lung diseases like pneumonia.
Q & A
Who discovered the antibacterial enzyme lysozyme?
-Alexander Fleming rediscovered lysozyme when he observed that a patient's mucus had killed bacteria in a culture.
How does lysozyme contribute to the immune system?
-Lysozyme acts as a key component in the body's first line of defense against bacteria by hydrolyzing the cell wall of bacteria.
What is the role of lysozyme as a hydrolytic agent?
-Lysozyme consumes water to break chemical bonds, particularly the glycosidic linkages of the bacterial cell wall, which are naturally very hard to break.
What are the two structural domains of the lysozyme molecule?
-Lysozyme has two structural domains: one composed of alpha helixes and the other composed mostly of beta strands.
How does lysozyme bind to the bacterial cell wall?
-Lysozyme binds specifically to the peptidoglycan strands of the bacterial cell wall and moves along the chain until the appropriate molecules are at its active site.
What are the two main residues that make up peptidoglycan strands?
-Peptidoglycan strands are comprised of two main residues: N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG).
Which two amino acids in lysozyme are crucial for breaking the glycosidic bond?
-Glutamate 35 and aspartate 52 are the two amino acids that play a vital role in breaking the glycosidic bond within the active site of lysozyme.
How does the mechanism involving glutamate and aspartate work to break the glycosidic bond?
-Glutamate acts as an electrophile, donating a proton to the glycosidic bond, allowing aspartate to act as a nucleophile and attack the bond, forming a glycosyl enzyme intermediate.
Why is the conformational change of the enzyme important in the lysozyme mechanism?
-The conformational change forces NAM into a half-chair conformation, which allows aspartate to be an efficient nucleophile by providing enough space for a direct backside attack.
How does the introduction of water after the intermediate stage contribute to the lysozyme mechanism?
-Water acts as a nucleophile to attack the carbon one of NAM, breaking the bond between the residue and aspartate and returning the enzyme to its relaxed state.
What is the significance of lysozyme in the immune system?
-Lysozyme is important because it weakens the structural integrity of bacterial cell walls by breaking the glycosidic bond between residues, leading to the death of bacteria.
In which bodily fluids is lysozyme found, and why is it valuable there?
-Lysozyme is found in bodily fluids such as tears, saliva, and mucus, where it acts as a first line of defense. It is also abundant in the blood to prevent bacteria from being transported throughout the body.
Outlines
🔬 Discovery and Function of Lysozyme
Alexander Fleming accidentally discovered lysozyme, an antibacterial enzyme, when a culture he was working on got mixed with a patient's mucus. This enzyme is part of the body's immune system and acts as a first line of defense against bacteria. Lysozyme works by hydrolyzing the cell wall of bacteria, which is a difficult process due to the strength of the glycosidic linkages in the peptidoglycan strands. The enzyme has a specific tertiary structure that binds to these strands, and its active site features two key amino acids, glutamate 35 and aspartate 52, which play a crucial role in breaking the glycosidic bond. This action weakens the bacterial cell wall, leading to the death of the bacteria. Lysozyme is particularly effective against gram-positive bacteria and is found in various bodily fluids, including tears, saliva, and mucus. It is also abundant in breast milk and egg whites, serving as a protective measure against harmful bacteria.
Mindmap
Keywords
💡Lysozyme
💡Penicillin
💡Peptidoglycan
💡Hydrolytic Agent
💡Glycosidic Bond
💡Active Site
💡Amino Acids
💡Electrophile
💡Nucleophile
💡Bacterial Cell Wall
💡Immune System
Highlights
Alexander Fleming discovered lysozyme when a culture sample got mixed with a patient's mucus, which killed the bacteria.
Lysozyme is an antibacterial enzyme that acts as a key component in the body's first line of defense against bacteria.
Lysozyme hydrolyzes the cell wall of bacteria, breaking the glycosidic linkages and weakening the structural integrity of the cell wall.
The enzyme has two structural domains - one composed of alpha helixes and the other mostly of beta strands, which together produce a tertiary structure.
Lysozyme binds specifically to the peptidoglycan strands of the bacterial cell wall and moves along the chain until it reaches the active site.
Peptidoglycan strands are made of N-acetyl muramic acid (NAM) and N-acetyl glucosamine (NAG), creating a sturdy cell wall via beta-1,4 linkages.
Glutamate 35 and aspartate 52 are two vital amino acids in the active site that interact with NAM and NAG to hydrolyze the glycosidic bond.
Glutamate acts as an electrophile, donating a proton to the glycosidic bond, allowing aspartate to act as a nucleophile and attack, breaking the bond.
The conformational change in NAM due to the enzyme's binding forces it into a half-chair confirmation, making aspartate an efficient nucleophile.
After the intermediate is produced, water is introduced as a nucleophile to attack and break the bond between the residue and aspartate.
Lysozyme is important because it weakens the bacterial cell wall, causing osmotic lysis and killing the bacteria.
Lysozyme is highly abundant in bodily fluids like tears, saliva, and mucus, where it serves as a first line of defense.
It is also found in high levels in breast milk and egg white, protecting the yolk from harmful bacteria.
While lysozyme is effective against gram-positive bacteria with peptidoglycan cell walls, it is less so with other types of bacterial cell walls.
Lysozyme is vital to the immune system of different organisms, especially newborns, as low levels increase the risk of lung diseases like pneumonia.
The study of lysozyme has contributed significantly to our understanding of proteins and enzymes.
Transcripts
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