Proteins that function as biological catalysts are known as enzymes (biocatalysts). Catalysts help to speed up chemical reactions. Substrates are the molecules upon which enzymes can operate, and the enzyme transforms the substrates into distinct molecules called products.
To happen at rates high enough to maintain life, almost every metabolic process throughout the cell involves enzyme catalysis. Enzymes are needed to catalyse each stage in metabolic pathways. Enzymology is the research of enzymes, and pseudo enzyme analysis is a modern area that recognises that certain enzymes have weakened their capacity to carry out biological catalysis over time, which is often expressed in their amino acid sequences and peculiar ‘pseudo catalytic’ properties.
Enzymes are known to catalyse over 5,000 different biochemical reactions. Ribozymes, which are catalytic RNA molecules, are another form of the biocatalyst. The specificity of enzymes stems from their three-dimensional structures.
Structure
Enzymes are globular proteins that can function individually or as part of larger complexes. The amino acid sequence determines the structure, and that in turn specifies the enzyme’s catalytic activity. Despite the fact that structure specifies the function, a novel enzymatic operation cannot still be predicted solely on the basis of structure. When enzyme structures are heated or subjected to chemical denaturants, they unfold (denature), and thus the structure is disrupted, resulting in a loss of operation.
Enzyme denaturation is usually associated with temperatures above a species’ normal range; as a result, enzymes from bacteria that live in volcanic settings, including hot springs, are coveted by industrial users for their ability to work at high temperatures, enabling enzyme-catalyzed reactions to run at a high rate.
Cofactors
Some enzymes don’t need any external components to function properly. Others involve the binding of non-protein molecules known as cofactors in order to work. Metal ions and iron-sulfur clusters are examples of inorganic cofactors, while organic compounds are examples of organic compounds (e.g., flavin and heme).
Metal ions, for example, can aid in the stabilisation of nucleophilic species within the active site. Coenzymes, which are extracted from the enzyme’s active site during the reaction, or prosthetic groups, that are closely attached to an enzyme, are examples of organic cofactors. Carbonic anhydrase, which includes a zinc cofactor bound as part of its active site, is an instance of an enzyme that requires a cofactor. Catalysis is catalysed by these closely bound ions or molecules, which are normally located in the active site. Redox reactions frequently involve flavin and heme cofactors, for particular.
Apoenzymes or apoproteins are enzymes that need a cofactor and do not have one attached to them. A holoenzyme is an enzyme that includes the cofactor(s) necessary for action (or haloenzyme).
The term holoenzyme may also refer to enzymes with several protein subunits, including DNA polymerases; in this case, the holoenzyme refers to the whole complex, which includes all of the subunits required for action.
Coenzymes
Small organic molecules which are loosely or closely bound to an enzyme are known as coenzymes. Chemical groups are transported from one enzyme to the next by coenzymes. NADPH, NADH, and adenosine triphosphate are some examples (ATP). Vitamins include several coenzymes, including thiamine pyrophosphate (TPP), flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN), and tetrahydrofolate (THF).
These coenzymes could not be produced by the body and therefore must be obtained via the diet in the form of highly associated compounds (vitamins). The following chemical groups are carried:
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NAD or NADP+ transports the hydride ion (H).
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Adenosine triphosphate holds the phosphate group.
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Coenzyme A carries the acetyl group.
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Folic acid carries the formyl, methenyl, or methyl groups
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S-adenosylmethionine carries the methyl group.
Factors Affecting Enzyme Activity
Below mentioned are the factors influencing enzyme activity:
Effect of Temperature on Enzyme Activity:
It is one of the factors that affect enzymes activity. The rate of an enzyme-catalyzed reaction increases as the temperature rises, as it does in all chemical reactions. At high temperatures, though, the rate drops again because the enzyme is denatured and no longer works. The amount of enzyme activity increases as the temperature rises. At the enzyme’s optimal temperature, maximum activity is achieved. If the temperature rises, the active site of the enzyme changes shape, resulting in a sudden decrease in activity. It has now been denatured.
Effect of pH on Enzyme Activity (pH and Enzyme Activity):
The form of an enzyme’s active site is also affected by changes in pH. Each enzyme performs better at a certain pH level. The optimal pH for an enzyme is determined by the condition in which it functions. The optimum pH of enzymes in the small intestine is around 7.5, but the optimum pH of enzymes in the stomach is about 2.
The intensity of enzyme activity increases as the pH rises. At the enzyme’s maximum pH, which in this case is pH 8, optimum activity is achieved. If the pH rises, the structure of the enzyme’s active site changes, resulting in a sudden decrease in activity. It has now been denatured.
Effect of Enzyme Concentration on Enzyme Activity:
As long as it is capable of binding, increasing the concentration of the enzyme will increase the rate of reaction. The reaction will no longer speed up once all of the substrates have been bound, as there will be nothing for additional enzymes to bind to.
Substrate Concentration on Enzyme Activity:
If there are plenty of substrates, enzymes can perform better. The intensity of enzyme activity increases as the substrate concentration rises. The rate of enzyme production, on the other hand, does not continue to rise indefinitely. This is because, despite the fact that there is plenty of substrate present, the enzymes will eventually become exhausted and no more substrates will suit at any given time. The intensity of enzyme activity increases as the substrate concentration rises. At the enzyme’s maximum substrate concentration, an optimum rate is achieved. Since there aren’t enough enzyme molecules to break down the excess substrate molecules, a sustained rise in substrate concentration results in the same behaviour.