Enzymes: Biological Catalysts and Their Functions

Enzymes play a crucial role in our bodies by facilitating biochemical reactions necessary for life, including digestion and protein synthesis. They are biological catalysts composed of proteins that accelerate chemical processes while remaining unchanged after the reaction takes place.

How do enzymes work? Enzymes lower the activation energy required for a reaction between substrates to occur, allowing reactions to happen more quickly and efficiently. Their activity is dependent on factors such as temperature, pressure, pH, and the presence of other molecules called inhibitors, which can slow down the rate of enzyme function. The process begins when substrates bind with the active site of the enzyme, creating an enzyme-substrate complex. This binding causes the enzyme's shape to change, known as conformational change, which stabilizes the transition state conformation of the reactant molecules. Once the substrates are positioned correctly within the active site, the enzyme promotes catalysis through formation of an intermediate, leading to product release followed by dissociation from the enzyme.

Types of Enzymes There are six main classes of enzymes, classified based on the type of bond they break, which determines their names:

1. Oxidoreductases - these enzymes facilitate redox reactions and are often referred to as oxidases or reductases, depending on whether they donate electrons (oxidase) or accept electrons (reductase).
2. Transferases - these enzymes move functional groups (like phosphate or glycosyl) from one molecule to another.
3. Hydrolases - these enzymes cleave bonds using water as the nucleophile.
4. Lyases - also known as lysases, these enzymes split bonds without water participation.
5. Isomerases - these enzymes convert one compound into another structural isomer.
6. Ligases - these enzymes incorporate two or more substrates together, forming covalent bonds.

Regulation of Enzyme Activity The activity of enzymes can be regulated through allosteric mechanisms and covalent modifications. Allosteric regulation involves modulating enzyme behavior through interaction with effector molecules that bind at non-catalytic sites on the enzyme, altering its shape and influencing its activity. Covalent modification includes reversible posttranslational modifications like phosphorylation, acetylation, methylation, deamination, glycosylation, carboxylation, and ADP ribosylation. These changes can either activate or inhibit enzyme function.

In summary, enzymes are essential biological catalysts that enable various biochemical processes. Understanding their structure, function, classification, and regulatory mechanisms is key to appreciating their significant roles in maintaining life.