Enzimi Biochimica - Tipologie e classi

Summary

This video script delves into the world of enzymes, highlighting their role as biological catalysts that speed up chemical reactions without being consumed. It categorizes enzymes into six classes based on the reactions they catalyze, such as oxidoreductases and transferases. The script further explains how enzymes function through energy changes and active site interactions, and how factors like substrate concentration, pH, and temperature influence their activity. It also touches on enzyme inhibitors, allosteric regulation, and covalent regulation, emphasizing the importance of enzymes in adjusting metabolic processes to cellular energy demands.

Takeaways

• 🧬 Enzymes are biological catalysts, which are proteins that speed up chemical reactions without being consumed in the process.
• 🔍 Enzymes selectively channel substrates in biochemical reactions, maintaining their structure and energy balance throughout the process.
• 📚 There are six classes of enzymes defined by the reactions they catalyze: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.
• 🍏 Oxidoreductases catalyze oxidation-reduction reactions, such as the conversion of lactate to pyruvate.
• 🔄 Transferases facilitate the transfer of functional groups like carbon, nitrogen, or potassium, exemplified by the conversion of serine to glycine.
• 💧 Hydrolases catalyze the breaking of bonds through the addition of water, playing a crucial role in digestion and other processes.
• 🔗 Lyases catalyze the breaking of various chemical bonds, including carbon-carbon, carbon-sulfur, and some carbon-nitrogen bonds.
• 🔄 Isomerases catalyze the transfer of atoms within a molecule to form isomeric forms, such as the conversion of malate to fumarate.
• 🔗 Ligase enzymes catalyze the formation of bonds between carbon, oxygen, nitrogen, and sulfur, often coupled with the hydrolysis of high-energy phosphates.
• 🔑 The function of enzymes can be influenced by energy changes and the stabilization of the transition state through various catalytic mechanisms.
• ⚗️ Factors affecting enzyme speed include substrate concentration, pH, and temperature, with enzymes having an optimal pH and temperature for activity.
• 🛑 Enzyme inhibitors can be reversible or irreversible, with competitive inhibition being a common type where the inhibitor binds reversibly to the active site.
• 🔄 Regulatory enzymes, or allosteric enzymes, adjust their catalytic activity in response to physiological signals and regulators, ensuring metabolic pathways adapt to cellular energy demands.

Q & A

What are enzymes and what is their primary function?

Enzymes are biological catalysts, which are proteins that increase the rate of chemical reactions without being consumed in the process. They remain unchanged after the reaction, allowing them to catalyze the reaction multiple times.

How do enzymes selectively channel substrates during their function?

Enzymes selectively channel substrates by binding to them in a way that is complementary in shape and charge, stabilizing the transition state of the reaction and thus facilitating the process without altering the substrate or enzyme itself.

What are the six classes of enzymes and what do they catalyze?

The six classes of enzymes are: Oxidoreductases (catalyze oxidation-reduction reactions), Transferases (catalyze the transfer of groups), Hydrolases (catalyze the breaking of bonds with the addition of water), Lyases (catalyze the cleavage of carbon-carbon, carbon-sulfur, and some carbon-nitrogen bonds), Isomerases (catalyze the transfer of atoms within a molecule to form isomers), and Ligases (catalyze the formation of carbon-oxygen, carbon-nitrogen, and carbon-sulfur bonds).

How do energy changes and the active site of an enzyme contribute to catalysis?

Energy changes involve the activation energy and the reaction speed, which are alternatives for the reaction. The active site of an enzyme is structured to bind only to a specific substrate, stabilizing it in its transition state and increasing molecular interactions, allowing the reaction to proceed correctly.

What are the three factors that influence the speed of an enzyme-catalyzed reaction?

The three factors influencing the speed of an enzyme-catalyzed reaction are substrate concentration, pH, and temperature. The reaction speed increases with substrate concentration until a maximum is reached, is optimal at a specific pH that reflects the environment where the enzyme functions, and increases with temperature until an inactivation point is reached.

What are enzyme inhibitors and how do they affect enzyme activity?

Enzyme inhibitors are molecules that interfere with catalysis by slowing down or blocking the reactions catalyzed by enzymes. They can be reversible, binding non-covalently and allowing the enzyme to resume activity once dissociated, or irreversible, rendering the enzyme permanently inactive.

What are the two common types of enzyme inhibition and how do they differ?

The two common types of enzyme inhibition are competitive inhibition, where the inhibitor binds reversibly to the site that the substrate should occupy, and non-competitive inhibition, where the inhibitor can bind to the enzyme or the enzyme-substrate complex, blocking the reaction without competing for the substrate binding site.

What are allosteric enzymes and how do they function?

Allosteric enzymes are enzymes that vary their catalytic activity in response to physiological signals through the action of regulators or modulators. They bind to these regulators in a site different from the active site, affecting the enzyme's activity and adjusting the speed of metabolic sequences to match cellular energy demands.

What are homotropic and heterotropic effectors, and how do they influence enzyme activity?

Homotropic effectors are substrate molecules that, when bound to an enzyme at a site different from the active site, increase the catalytic activity of other sites, cooperating with each other. Heterotropic effectors are different from the substrate and can influence enzyme activity in various ways, such as feedback inhibition, where the end product of a metabolic pathway inhibits an enzyme earlier in the pathway.

What are covalent regulators and how do they regulate enzymes?

Covalent regulators are enzymes that are regulated through the addition or removal of groups such as phosphate to specific residues like serine, threonine, and tyrosine. Phosphorylation and dephosphorylation, catalyzed by kinases and phosphatases respectively, are major cellular processes that regulate enzyme activity.

How do the levels of enzyme expression and activity regulation interplay?

Enzyme expression and activity regulation work on three levels: rapid and reversible activation/inactivation mechanisms, slower covalent modulation affecting enzyme activity, and gene expression that adjusts enzyme concentration in response to long-term exposure or specific conditions.