18. Biocatalysts – definition and structure of enzymes. Classification of the enzymes. Factors affecting enzyme activity – temperature, pH; influence of substrate concentration on the rate of enzymatic reaction – Michaelis-Menten constant. Zymogenes and isoenzymes. Specificity and regulation of enzyme activity - competitive and irreversible inhibitors.

Characteristics of Enzymes as Biological Catalysts

• Enzymes are biological catalysts that accelerate chemical reactions within cells by lowering the activation energy required for the reaction to occur. Key characteristics of enzymes include:

1. Specificity: Enzymes exhibit high specificity for their substrates, meaning they catalyze specific reactions involving specific substrates.
2. Efficiency: Enzymes significantly increase the rate of reaction without being consumed in the process, making them highly efficient catalysts.
3. Regulation: Enzyme activity can be regulated by various factors such as pH, temperature, substrate concentration, and allosteric effectors.
4. Reusability: Enzymes can catalyze multiple rounds of reactions and are not altered or consumed during the process.

Coenzymes and Prosthetic Groups

• Coenzymes: Coenzymes are organic molecules that assist enzymes in catalysis by carrying chemical groups between enzymes. Examples include NAD+, FAD, and coenzyme A.
• Prosthetic Groups: Prosthetic groups are non-protein molecules that are tightly bound to enzymes and are essential for their catalytic activity. Examples include heme in catalase and flavin mononucleotide (FMN) in succinate dehydrogenase.