Enzyme Research on Lactase in Humans

Enzymes are critical to all life on Earth, humans included. According to Cleveland Clinic (2021), enzymes are “proteins that help speed up chemical reactions in our bodies.” Enzymes build or break apart eaten substances, helping humans digest and metabolize the food that they eat. One such enzyme is lactase, which is an important enzyme that breaks down lactose from dairy foods like breast milk, cheese, and milk. Without enzymes, life would not be able to grow and survive.

Enzymes

As previously stated, enzymes are proteins that act as biological catalysts, speeding up chemical reactions in living organisms. Enzymes in a living organism reduce the amount of energy needed in the chemical reactions, allowing the body to house a wider range of reactions. This not only allows the organism to survive in harsher climates but also diversifies its food sources.

Lock and Key Model

In an enzyme-catalyzed reaction, the substrate, which is the molecule or molecules an enzyme acts upon, binds to the active site of the enzyme. The active site of an enzyme is the only place on an enzyme a substrate can bond to. This is due to the unique, 3-dimensional shape of each enzyme and molecule. This is known as the lock and key model. Similar to a “key into a lock, only the correct size and shape of the substrate (the key) would fit into the active site (the keyhole) of the enzyme (the lock)” (Lock-and-key model, 2022). Once snugly bonded, the enzyme assists in molding or breaking apart the substrate, creating a product to be used.

Figure 1

Lock and Key Model (lock and key model, 2022)

Note. A substrate (yellow) fits perfectly with an enzyme (blue). The jagged surface on the enzyme (blue) represents the active site. The substrate (yellow) fits perfectly in the active site.

Induced Fit

The induced fit model is the idea that enzymes are flexible and can change shape to better accommodate the substrate. Online Biology states that “both the substrate and the active site of the enzyme change in conformation until the substrate is completely bound to the enzyme” (Induced fit model, 2022). The weak interactions between the active site and the bonded substrate are what cause movement in the induced fit model (Enzymes, n.d.).

Figure 2

Induced Fit Model (induced fit model, 2022)

Note. Substrate 2 (green) does not bond perfectly with the enzyme (blue) at the active site. Substrate 2 (green) forces the enzyme (blue) to conform to its shape.

Lactase

The enzyme lactase is most known for being in LACTAID products, which help consumers digest lactose from dairy products. The word lactase is formed from the prefix lact-, meaning milk, and the suffix -ase, which is used to name enzymes.

Function and Location

Lactase catalyzes the hydrolysis reaction of its substrate lactose into glucose and galactose. The enzyme covalently bonds with the disaccharide lactose and assists with the breaking of the bonds between glucose and galactose. Due to its function, the lactase enzymes in the human body are mostly found in the small intestine, where they help digest the lactose found in dairy products consumed by humans. The enzymes preside in the villi of the cells lining the interior of the intestine and are either secreted into the digestive tract or bound to the apex of villi.

Survivability Regarding Temperature and Acidity

The range of survivability regarding temperature is between 70 and 120 degrees Fahrenheit, with the optimal temperature being 115 degrees. If the temperature is too low, lactase efficiency slows. If the temperature is too high, the enzyme denatures. The optimal acidity level for lactase is 6 pH, with a range between 2 and 7. Environments outside of this range will cause the enzyme to denature. When an enzyme denatures, it loses its shape, thereby losing the ability to bond with a substrate and catalyze a reaction.

Inhibitors

Known natural inhibitors of lactase are glucose and galactose, which are the products related to the enzyme. Therefore, the enzyme lactase is affected by feedback inhibition, as the products are its own inhibitors. Brenda (2023) further states that “galactose is a competitive 4 inhibitor... while glucose is a noncompetitive inhibitor.” An artificial inhibitor is O-nitrophenyl-beta-D-galactopyranoside, or ONPG. The structure of ONPG is similar to that of lactose and acts as a competitive inhibitor.

Work Cited

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Biology Online. (2022, June 16). Induced fit model. Biology Articles, Tutorials & Dictionary Online. Retrieved April 25, 2023, from https://www.biologyonline.com/dictionary/induced-fit-model

Breda, J. (2023, February 1). In vitro analysis of lactase activity in commercial probiotics. Westminster College. Retrieved April 25, 2023, from https://westminstercollege.edu/student-life/the-myriad/in-vitro-analysis-of-lactase-activit y-in-commercial-probiotics.html

Cleveland Clinic. (2021, May 12). Enzymes: What are enzymes, pancreas, digestion & liver function. Cleveland Clinic. Retrieved April 25, 2023, from https://my.clevelandclinic.org/health/articles/21532-enzymes

Gitonga, M. (2023, January 4). Enzyme lactase- definition, function, & Location/Production. Tutorsploit. Retrieved April 25, 2023, from https://www.tutorsploit.com/biology/enzyme-lactase-definition-function-location-product ion/

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Merriam-Webster. (n.d.). Substrate. In Merriam-Webster.com dictionary. Retrieved April 25, 2023, from https://www.merriam-webster.com/dictionary/substrate

Reynolds, J. (2021, August 1). 42: Beta-galactosidase test (ONPG). Biology LibreTexts. Retrieved April 25, 2023, from https://bio.libretexts.org/Learning_Objects/Laboratory_Experiments/Microbiology_Labs/ Microbiology_Labs_I/42%3A_Beta-Galactosidase_Test_(ONPG)

Siskin, T. J. (2017, November 21). The effects of ph and temperature on enzyme activity of lactase on lactose. Education. Retrieved April 25, 2023, from https://education.seattlepi.com/effects-ph-temperature-enzyme-activity-lactase-lactose-70 34.html

UC Scouts. (n.d.). Enzyme Regulation. ucscout. Retrieved April 25, 2023, from https://classroom.ucscout.org/courses/18370/pages/video-7-dot-04-enzyme-regulation?m odule_item_id=1806126

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