Enzymes are proteins that help speed up metabolism or the chemical reactions in our bodies. They are also known as biocatalysts because enzymes speed up biochemical reactions in living organisms. Enzymes build some substances or break others down. They are made of strings of amino acids chemically bonded to one another, and this bonding gives enzymes a unique structure that determines their function. Human bodies produce enzymes naturally but can also be manufactured in food and other products.
Enzymes are so necessary for digestion, the functioning of the liver, and other functions. Healthcare givers can detect injuries and diseases in our bodies by the use of enzymes. They help in the process of digestion. This process is made possible by the enzymes present in the saliva, such as saliva amylase, intestines, and pancreas. These enzymes break down fats, protein, and carbohydrates. They are also responsible for creating chemical reactions in the body that speed up the rate of a chemical reaction to help support life.
Essential tasks performed by enzymes include the following:-building muscle, destroying toxins, and breaking down food particles during digestion. They are not reactants and are not used up during the reaction. Once an enzyme binds to a substrate and catalyzes the reaction, the enzyme is released, unchanged, and can be used for another reaction.
Enzymes are produced naturally in the body. It can also be gotten in fruits, vegetables, other foods, and supplements. Too much or too little of certain enzymes in the body can cause health problems. People with problems such as pancreatitis, cystic fibrosis, or pancreatic cancer have reduced the body’s essential enzymes. People with these conditions are subjected to dietary enzymes pills, which are a supplement. Enzymes catalyze all kinds of chemical reactions involved in the growth, blood coagulation, healing, diseases, breathing, digestion, reproduction, and many other biological activities.
Types of enzymes
There are different types of enzymes. These are:
- Oxidoreductases – these enzymes speed up redox reactions and are further divided into oxidase and reductase.
- Hydrolases – they speed up the hydrolysis of the substrates.
- Lyases – these enzymes promote eliminating a group from the substrate to leave a double bond reaction or speed up a reverse response.
- Ligases – these enzymes speed up the reaction of two molecular substrates into one molecular compound hence producing energy.
- Translocase – these enzymes speed up the reaction of ions moving across a membrane.
- Isomerase – These groups of enzymes accelerate the conversion of isomers.
- Transferases – these enzymes speed up the transfer of a group among other substrates.
There are three main types of digestive enzymes. These are:
a). Amylase is produced in the mouth, and it breaks down starch and carbohydrate into sugar.
b). Protease –it is produced in the stomach, pancreas, and small intestine. It breaks down proteins into amino acids.
c). Lipase –it is produced in the pancreas and small intestine. It breaks down lipids which are fats and oils, into glycerol and fatty acids. A particular type of Lipase is found in breast milk to aid a baby easily to digest fat when nursing.
Characteristics of enzymes.
- Enzymes are proteins in nature; therefore, they are folded like chains of amino acids with a specific shape. These shapes are determined by the sequence of amino acids held together by a bond.
- Enzymes speed up reactions by bringing reactants together and reducing the activation energy required to start the reaction.
- Enzymes are specific since they have a particular shape, and only a specific substrate will fit its active site.
- They are affected by heat and temperature –enzymes will be inactive under low temperature, while the enzymes will be denatured at a higher temperature.
- Some require coenzymes – enzymes do not work alone they need a helper molecule.
- Enzymes are affected by Ph – some enzymes will be active in acidic pH, some will be active in alkaline Ph, and others will be active in neutral.
- Some of the enzymes catalyzed reactions can be reversible, while some are not reversible.
- Enzymes remain unchanged during the reaction itself.
- All enzymes are made up of protein.
- All enzymes speed up the reaction.
- All enzymes are specific in action.
- All enzymes do not get used up during the reaction.
Allosteric enzymes
Allosteric enzymes are enzymes that alter their conformational ensemble upon binding of an effector, which results in an apparent change in binding affinity at a different ligand-binding site.
An allosteric site does not bind substrate but instead binds another molecule that affects the enzyme’s regulation. When a molecule binds an allosteric site, it alters the shape of the enzyme.
Allostery is the process of enzyme regulation, where binding at one site influences the binding at subsequent sites.
Allosteric enzymes are activated by substances produced in the pathway in which the enzymes function. These substances are called modulators and can alter the activity of allosteric enzymes by changing their conformation.
Allosteric enzymes are larger and more complex than non-allosteric enzymes and often have many sub-units.
Enzymes with more than one effector have different and specific binding sites for each one. Mostly allosteric enzymes, the substrate-binding site, and the effector binding site are on various substrates.
Our bodies have various regulatory measures that control all processes and respond to multiple internal and external environment changes.
Examples of allosteric enzymes are:-
a). Glucokinase– plays a vital role in glucose homeostasis by converting glucose to glucose-6-phosphate and enhanced glycogen synthesis in the liver.
b). Acetyl-CoA Carboxylase- it regulates the process of lipogenesis. It is activated by citrate and inhibited by a long chain acyl-CoA molecule.
c). Aspartate Transcarbamolylase (ATCase), which catalyzes the biosynthesis of pyrimidine.
Characteristics of allosteric enzymes
- Allosteric enzymes have active and inactive shapes differing in 3D structure.
- Allosteric enzymes have multiple inhibitor binding sites involved in switching between active and inactive shapes.
- Allosteric enzymes have a characteristic ‘S’ – shaped curve for reaction rate verse substrate concentration.
- Allosteric enzymes can respond to multiple conditions that influence biological reactions.
- Allosteric enzymes are the biological catalyst that increases the rate of the reaction.
- The binding of the effector molecule changes the conformation of the enzyme.
- Activator increases the activity of an enzyme, whereas inhibitor decreases the activity after binding.
Allosteric enzymes regulation mechanism.
Allosteric regulation is the process of modulating the activity of a protein by binding a ligand, called an effector, to a site topographically distinct from the site of the protein, called the active site, where the activity characterizing the protein is carried out.
Allosteric regulation of enzymes is vital for the control of cellular metabolism. Allosteric regulation occurs when an enzyme’s activator or inhibitor molecule binds at a specific regulatory site and induces conformational or electrostatic changes that enhance or reduce activity.
There are two types of allosteric regulation based on substrate and effector molecules:
Homotropic regulation –the substrate molecule acts as an effector. Mostly it is enzyme activation and also called cooperativity.
Heterotrophic regulation –when the substrate and effector are different, the effector may activate or inhibit the enzyme.
Allosteric inhibition –when an inhibitor binds to the enzyme, all the protein complex active sites undergo conformational changes to decrease the enzyme’s activity.
Allosteric activation –when an activation binds, it increases the function of active sites and results in increased binding of substrate molecules.
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