Understanding the role of individual components in a biological system is an important step to elucidate or predict its behavior. However, a major theme in systems biology is investigating these systems with an integrated approach. In fact, studying the interactions between different components also gives insights into the functioning and behavior of the components taken independently. Each enzyme is able to promote only one type of chemical reaction.
Some enzymes help to break down large nutrient molecules, such as proteins, fats, and carbohydrates, into smaller molecules. Enzymes operate in tightly organized metabolic systems called pathways. They are vital for life and serve a wide range of important functions in the body, such as helping in digestion and metabolism.
Examples
Lipases is a group of enzymes that help digest fats in the gut.
Amylase helps change starches into sugars. Amylase is found in saliva.
Maltase is found in saliva; breaks the sugar maltose into glucose. Maltose is found in foods such as potatoes, pasta, and beer.
Trypsin is found in the small intestine, breaks proteins down into amino acids.
Lactase is found in the small intestine, breaks lactose, the sugar in milk, into glucose and galactose.
Acetylcholinesterase breaks down the neurotransmitter acetylcholine in nerves and muscles.
Helicase unravels DNA.
DNA polymerase synthesize DNA from deoxyribonucleotides.
Other enzymes guide the smaller, broken-down molecules through the intestinal wall into the bloodstream. Still other enzymes promote the formation of large, complex molecules from the small, simple ones to produce cellular constituents. Enzymes are also responsible for numerous other functions, which include the storage and release of energy, the course of reproduction, the processes of respiration, and vision. They are indispensable to life.
Enzymes play an increasingly important role in medicine. The enzyme thrombin is used to promote the healing of wounds. Other enzymes are used to diagnose certain kinds of disease, to cause the remission of some forms of leukemia, a disease of the blood-forming organs and to counteract unfavourable reactions in people who are allergic to penicillin. The enzyme lysozyme, which destroys cell walls, is used to kill bacteria. Enzymes have also been investigated for their potential to prevent tooth decay and to serve as anticoagulants in the treatment of thrombosis, a disease characterized by the formation of a clot, or plug, in a blood vessel. Enzymes may eventually be used to control enzyme deficiencies and abnormalities resulting from diseases.
Enzymes can be regulated by changing the activity of a preexisting enzyme or changing the amount of an enzyme.
Changing the activity of a pre-existing enzyme: The quickest way to modulate the activity of an enzyme is to alter the activity of an enzyme that already exists in the cell.
Substrate availability
Product inhibition
Allosteric regulation
pH and enzyme conformation
pH and active site protonation state
Covalent modification
2. Changing the amount of an enzyme: Another and less immediate but longer duration method to modulate the activity of an enzyme is to alter the activity of an enzyme that already exists in the cell.
Alternation in transcription of enzyme's gene
Degradation of messenger RNA for the enzyme
Co/Post translational changes
Functions
Signal Transduction
Macromolecules Degradation
Energy Generation
Ion Pumps
Defense and Clearance
Cell Regulation
In addition, enzymes are also able to generate movement, with myosin hydrolyzing ATP to generate muscle contraction, and transport intracellular substances around the cell as part of the cytoskeleton. Enzymes are important players in many other functions, including immune responses and aging processes. Luciferase is the major reason for the glowing of fireflies, and enzymes in virus are involved in infecting cells or the release of virus particles from host cells.
