Where is lactase synthesized

This leads to gas build-up in the gut, resulting in cramping and flatulence. In the case of lactase persistence, there is a continued production of lactase at high levels throughout adulthood. Why is the production of lactase regulated in the first place? Why not just produce lactase in the enterocytes of all adult mammals? The answer is a matter of cellular energetics.

Most mammals humans notwithstanding do not consume milk after they have been weaned. Therefore, the energy invested in biosynthesizing lactase is an unnecessary expenditure.

The LCT gene mutations change single protein building blocks amino acids in the lactase enzyme or result in an enzyme that is abnormally short. The mutations are believed to interfere with the function of the lactase enzyme, leading to undigested lactose in the small intestine and causing severe diarrhea.

Lactose intolerance in adulthood is caused by gradually decreasing activity expression of the LCT gene after infancy, which occurs in most humans.

Genetics Home Reference has merged with MedlinePlus. Learn more. The information on this site should not be used as a substitute for professional medical care or advice. Babies that are born on time, not too early, make lots of lactase and can readily digest milk.

However, as they become adults, their small intestine can stop producing lactase altogether resulting in lactose intolerance.

In addition to intestinal cells, certain bacteria that live in the intestine also make the lactase enzyme. Lactose that is not digested by human lactase is digested by bacterial lactase. When bacteria are ingested as part of food yogurt , the lactase enzyme survives the acid stomach because it is protected by the bacterial cell wall.

Once in the small intestine, the bacteria release the lactase enzyme to digest lactose. An intact bacterial cell wall, which surrounds the entire bacterium, and the rate of lactase release are the two factors that determine how well a treatment of lactose intolerance by yogurt ingestion will be. People who are lactose intolerant can obtain lactase by taking it in the form of a pill or chewable tablet.

WebMD recommends that tablets containing 6,, IU international units should be ingested at the start of a meal. It also recommends adding 2, IU of liquid lactase to a milliliter cup of milk right before drinking it. Finally, a vesicle containing mature lactase travels from the Golgi Apparatus to fuse with the external brush border membrane of epithelial cell.

Here, the enzyme will carry out its function of breaking down dietary lactose. The regulation of lactase synthesis over developmental time is the factor that separates lactase persistent from non-persistent individuals. This is because mammals don't typically consume milk in adulthood, so the production of enzymes to help digest milk is unnecessary and therefore energetically wasteful at a cellular level.

Age-dependent lactase regulation of this sort occurs at transcription. A transcription factor TF is a protein that binds to a specific segment of DNA and influences a gene's transcription frequency. Once bound to DNA, a TF either attracts or repels the molecular machinery necessary for transcription.

TFs can even attract other transcription factors to form large transcription complexes.