Factors that influence enzyme activity
According to a research made by Shrief in 2020, enzymes make chemical reactions finish faster. These enzymes are affected by 5 factors which are: temperature, pH, concentration, inhibitors and water.
Temperature:
Starting with the first factor, temperature, depending on the type of protein the enzyme is formed, the optimal temperature can vary between 37 and 40 degrees Celsius (Shrief, 2020). Under extreme temperature, enzymes can lose activity but there are a few exceptions, for example TsLI isomerase works at above 95 °C (Mesbah, 2021).
However, some enzymes that come from hyperthermophilic organisms still work even at temperatures above 100 °C (Unsworth, van der Oost and Koutsopoulos, 2007). These enzymes are very heat-stable because of several special features working together, not just one (Unsworth, van der Oost and Koutsopoulos, 2007). Their stability comes from things like strong internal bonds that hold the protein together, tightly packed structures that make it harder to fall apart, and fewer flexible or loose parts that could break down at high temperatures (Unsworth, van der Oost and Koutsopoulos, 2007). Some of these enzymes are made up of several connected subunits, which helps them stay stable when it’s really hot (Unsworth, van der Oost and Koutsopoulos, 2007). Even though this rigid structure helps them survive heat, it also means they may not work as well at lower temperatures, since they can’t move as easily to carry out reactions (Unsworth, van der Oost and Koutsopoulos, 2007). Because they can stay active at very high temperatures where normal enzymes would stop working, hyperthermophilic enzymes are useful in industries that run processes under extreme heat (Unsworth, van der Oost and Koutsopoulos, 2007).
Some microorganisms, called psychrophiles, live in extremely cold places like the deep ocean or polar regions (Hamid et al., 2022). They produce cold-active enzymes that can work well even at temperatures near freezing, while most normal enzymes would stop working (Hamid et al., 2022). These enzymes are able to function in the cold because they have more flexible structures and weaker internal bonds, which let them move and react easily at low temperatures (Hamid et al., 2022). However, this flexibility also means they can lose stability and stop working when it gets warmer (Hamid et al., 2022). Cold-active enzymes are useful in many industries, such as food production, medicine, and environmental cleanup, because they work at low temperatures without needing extra heat (Hamid et al., 2022). This saves energy and helps protect heat-sensitive materials (Hamid et al., 2022). Scientists are now studying and improving these enzymes through protein engineering so they can be used more widely and effectively (Hamid et al., 2022).
pH:
The next factor is pH, each enzyme works at around 7.5 (Shrief, 2020). If that pH isn’t reached, the enzyme won’t work with the best efficiency (Shrief, 2020). We have some exceptions here as well, Bifunctional Man/Cel5B has maximal activity at pH 5.5 and Nitphym who has a very large range (Mesbah, 2021). Each enzyme has its own specific optimum pH, which can vary widely, some enzymes work best in very acidic conditions, around pH 2–3, while others prefer strongly basic conditions, up to pH 9–10. Changes in pH affect the charges on both the enzyme’s amino acid side chains and the substrate, which can change how well the substrate fits into the enzyme’s active site. Extreme pH levels can distort or even denature the enzyme’s three-dimensional structure, permanently destroying its activity. Enzymes that rely mainly on uncharged groups tend to have a broader pH range in which they can function, while enzymes that use charged groups have a narrower pH range and quickly lose activity if the pH shifts. For example, acid phosphatase works best at pH 3.8 and alkaline phosphatase at pH 9.5; although both are found in blood plasma, they are not active at the normal body pH of 7.4. In laboratory experiments, enzyme activity should always be measured at or near the optimum pH, because testing too far from that value gives inaccurate results. Small pH differences, such as ±0.1 units, usually do not significantly affect enzyme activity, but larger shifts can have a strong impact [5].
Concentration:
Now on the concentration factors, there are 2 types that can influence the reactions: substrate and enzyme (Shrief, 2020). If the substrate concentration rises, the reaction rate increases until it reaches a limit (Shrief, 2020). At this point, all enzyme active sites are occupied, meaning the enzymes are saturated (Shrief, 2020). If the enzyme concentration is boosted, the reaction rate is sped up as long as substrate is present to bind (Shrief, 2020). However, once all substrate molecules are occupied, adding more enzymes will have no further effect (Shrief, 2020). Extremozymes, on the other hand, are much more tolerant (Mesbah, 2021). For example, the enzyme Nitphym nitrilase was shown to keep working even when exposed to very high substrate concentrations up to 500 mm of nitriles, a level that would normally deactivate many regular enzymes (Mesbah, 2021).
Inhibitors:
There are 2 types of inhibitors that can influence the function of the enzyme: competitive and non-competitive inhibitors (Shrief, 2020).
Water:
Enzymes need a certain level of hydration to become active (Shrief, 2020). They usually stop working or lose their shape when they are exposed to water (Mesbah, 2021). This is because the solvents interfere with the weak bonds that hold the enzyme’s structure together, causing it to unfold and lose its activity (Mesbah, 2021).
In food preservation it is essential to fully suppress enzymatic activity when storage temperatures fall below the phase transition point (Shrief, 2020).
References (5):
1. Shrief, E. (2020). Factors Affecting Enzyme Activity. [online] ResearchGate. Available at: https://www.researchgate.net/publication/347439618_Factors_Affecting_Enzyme_Activity.
2. Mesbah, N.M. (2021). Editorial: Enzymes From Extreme Environments, Volume II. Frontiers in Bioengineering and Biotechnology, 9. doi:https://doi.org/10.3389/fbioe.2021.799426.
3. Unsworth, L.D., van der Oost, J. and Koutsopoulos, S. (2007). Hyperthermophilic enzymes−stability, activity and implementation strategies for high temperature applications. FEBS Journal, 274(16), pp.4044–4056. doi:https://doi.org/10.1111/j.1742-4658.2007.05954.x.
4. Hamid, B., Bashir, Z., Yatoo, A.M., Mohiddin, F., Majeed, N., Bansal, M., Poczai, P., Almalki, W.H., Sayyed, R.Z., Shati, A.A. and Alfaifi, M.Y. (2022). Cold-Active Enzymes and Their Potential Industrial Applications—A Review. Molecules, [online] 27(18), p.5885. doi:https://doi.org/10.3390/molecules27185885.
5. https://www.ucl.ac.uk/~ucbcdab/enzass/pH.htm
6. Sonia Del Prete and Pagano, M. (2024). Enzyme Inhibitors as Multifaceted Tools in Medicine and Agriculture. Molecules, [online] 29(18), pp.4314–4314. doi:https://doi.org/10.3390/molecules29184314.
