> See also: > - [[Chemical Reactions|Catalysts]] > - [[Activation Energy and the Reaction Coordinate]] > - [[Enzyme Kinetics]] # Enzymes Enzymes are macromolecular structures ([[proteins]] or [[Ribonucleic Acid (RNA)|RNA]]) which lower the activation energy necessary for biological reactions. - They are essential for regulating the rate at which chemical reactions occur within organisms - By lowering the activation energy of a reaction, the enzyme will increase the speed at which Unlike proteins, enzymes are often names based on how they catalyze reactions --- There are two main models of enzyme-substrate interactions ## Enzyme Cofactors - Enzymes can also use cofactors to further stabilize the reactions their catalyze - Prosthetic groups are tightly associated with the enzyme polypeptide chain ![[Pasted image 20231027085620.png|300]] | Type | Description | Examples | | ---- | ---- | ---- | | Cofactor | | | | Metal Ions | | | | Coenzymes | | | | Cosubstrates | | | | Prosthetic Groups | | | **Apoenzymes** (or apoproteins) are enzymes that require a cofactor but do not have one bound. ## Enzyme Classifications & Mechanisms | Enzyme Class | Type of Enzyme | Reaction Catalyzed by Enzyme | Examples | | ---- | ---- | ---- | ---- | | EC 1 | Oxidoreductase | Oxidation-reduction reactions | Alcohol Dehydrogenase | | EC 2 | Transferases | Transfer of functional groups | DNA Polymerase | | EC 3 | Hydrolases | Hydrolysis reactions | Actin, Elastase | | EC 4 | Lyases | Group elimination to form double bonds | | | EC 5 | Isomerases | Isomerization | | | EC 6 | Ligases | Bond formation coupled with ATP hydrolysis | | | EC 7 | Translocases | Assists in moving another molecule (typically across a membrane) | ATP Synthase | > Translocases are a relatively new enzyme class Enzymes bring substrates together at a specific location in the enzyme called the **active or catalytic site** in order to form an enzyme-substrate complex - Induced fit model ### Additional Types of Enzymatic Activity - Kinases - Recombinases - Resolvases ## Enzyme Strategies - Acid-base catalysis - Covalent catalysis - Metal catalysis - Proximity and orientation effects - Preferential binding to the transition state complex An enzyme may use any combination of these strategies to achieve its higher reaction rates, however, most enzymes will share the strategy of preferentially binding to transition state complexes. ## Enzyme Regulation The rate of an enzyme-catalyzed reaction can be affected by either ### Enzyme Inhibition A competitive inhibitor directly competes with the substrate at an enzyme’s active site and prevents it from forming the typical product A non competitive inhibitor affect enzyme activity by binding to the enzyme at a location that is not the active site. In this process, it can alter the enzyme’s shape, making it less active or fully inactive. - Frequently heavy metals such as mercury noncompetitive inhibition is a type of allosteric regulation? Types of Inhibition - Competitive - Uncompetitive - Mixed - Pure noncompetitive (a special case of mixed inhibition) - Irreversible (inactivation) ### Enzyme Saturation > [!question] enzyme concentration > enzymes are almost always significantly larger than the molecules they are interacting with > what is the concentration of enzymes within an environment vs the concentration of the molecules undergoing the reaction? > - similar question for hemoglobin, such a large structure is used to transport individual atoms (oxygen) > - I think the key feature is the ability to bind and UNBIND the oxygen. There’s going to be oxygen throughout our bodies (water is our solvent) but it does not readily unbind from these molecules and therefore isn’t a viable source to be used in biochemical reactions > - (still wondering about the transportation aspect, I think something about concentration gradients and the interactions between both myoglobin and hemoglobin answer this though) ### Effects of Substrate Concentration > [!NOTE] **Michaelis Constant** > Contents ![[Enzyme Shtuff.pdf]] ``