40 by: Yevgeniya Bukina
Student: Yevgeniya Bukina
Enzyme: Lactase
EC 3.2.1.108
Where is lactase found? Lactase is produced on the brush border of the small intestine of mammals by cells called enterocytes. The brush border is a group of microvilli, small, finger-like projection. When nutrients pass through the small intestine, they are absorbed by the microvilli.
What does the lactase do? Lactase breaks down lactose, a sugar contained in milk and some other dairy products, for example cheese, yoghurt and cream. It breaks it down to glucose and galactose, to ease the absorption process. When there are mutations in the gene that codes for lactase leads to the insufficient production of the enzyme. This, in turn, results in the inability to break down lactose, so the person is lactose intolerant. Lactose intolerance manifests as intestinal distress and production of gas, because the lactose is fermented by bacteria.
Interesting facts about lactase:
- 1) In humans, it is most active in infancy, while the main source of nutrients for the child is milk, but then the production levels decrease.
- 2) Most mammals besides humans stop producing it once they are weaned off mother’s milk.
References:
1) 3.-.-.- Hydrolases | 3.2.-.- Glycosylases | 3.2.1.- Glycosidases, I.e. Enzymes Hydrolyzing O- and S-Glycosyl Compounds. Pubchem.ncbi.nlm.nih.gov. Retrieved from https://pubchem.ncbi.nlm.nih.gov/protein/EC:3.2.1.108
2) Forsgård, R.A. Lactose digestion in humans: intestinal lactase appears to be constitutive whereas the colonic microbiome is adaptable. Am J Clin Nutr. 2019 Aug 1. PMID: 31175813; PMCID: PMC6669050. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6669050/#:~:text=Lactase%2Dphlorizin%20hydrolase%20(LPH),ileum%20(1%2C%202).
3) Lactase: Uses, Side Effects, Interactions, Dosage, and Warning. Webmd.com. 2019. Retrieved from https://www.webmd.com/vitamins/ai/ingredientmono-540/lactase
4) LCT Gene: MedlinePlus Genetics. Medlineplus.gov. 2020 Aug 18. Retrieved from https://medlineplus.gov/genetics/gene/lct/#:~:text=Normal%20Function&text=This%20enzyme%20helps%20to%20digest,finger%2Dlike%20projections%20called%20microvilli
5) Encyclopedia Britannica. Lactase | Enzyme. Encyclopædia Britannica. 2014 Nov 17. Retrived from https://www.britannica.com/science/lactase
6) Wiley, A.S. Lactose intolerance. Evol Med Public Health. 2020 Feb 17. PMID: 32211192; PMCID: PMC7081935. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC7081935/
7) Fernandez, P., Cañada, F.J., Jiménez-Barbero, J., Martín-Lomas, M. Substrate specificity of small-intestinal lactase: Study of the steric effects and hydrogen bonds involved in enzyme-substrate interaction. Carbohydrate Research. 1995. Retrieved from https://doi.org/10.1016/0008-6215(95)00034-Q.
8) Rocha, J., Guerra, A. On the valorization of lactose and its derivatives from cheese whey as a dairy industry by‑product: an overview. European Food Research and Technology. 2020. Retrieved from https://www.researchgate.net/publication/343472413_On_the_valorization_of_lactose_and_its_derivatives_from_cheese_whey_as_a_dairy_industry_by-product_an_overview
9) PBD Protein Data Bank. RCSB PDB – 8Q7Y: ESIBD structure of beta-galactosidase. Rcsb.org. 2023. Retrieved from https://www.rcsb.org/structure/8Q7Y
10) Beta-Lactose. PubChem. 2019. Retrieved from https://pubchem.ncbi.nlm.nih.gov/compound/beta-Lactose
11) High Plains Surgical Associates. Small Bowel. High Plains Surgical Associates. Retrieved from highplainssurgical.com/small-bowel.
