Lactase: Definition, Structure And Its Various Intolerance

Lactase Definition

Lactase is a digestive enzyme which aids in the digestion of lactose, a sugar present in milk, in the small intestines of mammals. When the offspring are weaned and can take other meals, lactase activity drops, which is why animals need milk to nourish their young. Lactose persistence (a.k.a. lactose tolerance), or the ability to digest milk into maturity, is a genetic mutation, while lactose intolerance is the “normal” condition in humans and other animals after infancy.

Function of Lactase

Lactase’s function is to degrade lactose into its two simple sugar components: glucose and galactose. Lactose may be absorbed and utilised by the body when it is broken down into simple sugars in the small intestine. If lactose is not broken down, it will pass through the digestive system unabsorbed.

Infant animals rely only on the sustenance provided by their mother’s milk. Lactase activity is increased throughout infancy to ensure that the body can acquire nutrients from this key dietary source. Lactase activity decreases when a young animal is weaned from milk. Lactase is not necessary when milk production declines as a result of decreased consumption. Lactase production in humans starts to decline at the age of four. However, some people have a lactose tolerance and may continue to generate lactose even after they reach adulthood.

Structure of Lactase

Lactase is produced by a gene on chromosome 2 in humans. Pre-pro-lactase is the first polypeptide, or sequence of amino acids, produced by that specific gene. Pre-pro-lactase has a 1,927 amino acid sequence. Segments of the polypeptide chain are eliminated during the lactase maturation process. Lactase is made up of four identical subunits and a large number of chains. Each component has 1023 amino acid residues, totalling 4092. Lactase is a homotetramer, consisting of four identical subunits.

Lactose Intolerance

Primary Lactose Intolerance

The most common kind of lactose intolerance is primary lactose intolerance. Hypolactasia is a term that is often used to refer to lactose intolerance. Adults are unable to digest lactose owing to a lactase production deficit. Primary lactose intolerance is quite common around the globe; 70% of individuals are lactose intolerant after infancy. Around a third of the US population suffers from lactose intolerance. Because a significant proportion of the population in the United States is now of European heritage, where lactose persistence rates are rather high, this percentage is nevertheless lower than in a number of other nations.

Lactose intolerance affects the great majority of people in Asia, certain parts of Africa, and Southern Europe, as well as the large majority of Native Americans. While newborns and children are capable of consuming milk and other dairy products, their bodies progressively lose the capacity to digest lactose. Lactose intolerance may develop over a period of up to twenty years.

Lactose intolerance symptoms begin to develop within a few hours after dairy product use. Vomiting, cramps, gas, diarrhoea, and dyspepsia are just a few of the symptoms. While there is no method to increase the quantity of lactase generated by the body, there are a few therapy options for lactose intolerance. Lactase drops or capsules are available over-the-counter and may be used to augment the lactase necessary for digestion prior to consuming dairy products.

Consuming dairy in moderation and just during meals may help alleviate symptoms. For example, a modest quantity of milk ingested during a meal may not induce gastrointestinal irritation. Additionally, the degree of symptoms is determined by the kind of dairy ingested. Yogurt and hard cheeses contain lactose-digesting bacteria and hence produce fewer symptoms than other dairy products.

Secondary Lactose Intolerance

Lactase production is impaired as a consequence of damage or infection to the small intestinal lining, resulting in secondary lactose intolerance. Lactose intolerance is a possibility as a result of Celiac disease, surgery, bacterial overgrowth, or Crohn’s disease. This problem may be treated by treating the underlying sickness or injury that caused the intolerance. When the underlying illness or injury is corrected, the lactose intolerance symptoms subside as well.

Congenital Lactose Intolerance

Lactose intolerance is a very uncommon condition. It is an autosomal recessive illness in which a baby is born unable to digest lactose due to an inadequate amount of lactase produced by the body. This is a serious worry since infants only ingest milk! However, it may be addressed by giving lactose-free formula to the infant. Due to its inability to digest lactose, a baby who does not get lactose-free formula but rather breast milk or conventional formula may undergo severe water loss and weight loss.

Related Biology Term

  • Lactose: Sometimes referred to as “milk sugar,” lactose is a sugar made up of glucose and galactose that is broken down by the enzyme lactase.
  • Enzymes: Enzymes are proteins that catalyse chemical reactions.
  • Polypeptide: A polypeptide is a molecule composed of a long chain of amino acids.
  • Digestion: Digestion is the process by which food is broken down in order for it to be absorbed and utilised by the body. 


1, When does lactase production decrease in mammals?

  1. Around the age of four,
  2. When the mammal is weaned,
  3. When the mammal reaches adulthood,
  4. Lactase production does not decrease in mammals.

Answer to Question #1

B is correct. In mammals, lactase production normally begins to decrease when a mammal is weaned and begins to consume foods other than milk. In humans, this occurs slightly later, around the age of four (except in humans with lactose persistence).

2. How can the symptoms of lactose intolerance be reduced?

  1. Taking lactose-containing capsules
  2. Avoiding/minimizing the amount of dairy consumed
  3. Consuming certain dairy products over others, like yogurt,
  4. All of the above

Answer to Question #2

D is correct. There is no cure for lactose intolerance, but all of the above choices can be implemented in order to reduce the symptoms of lactose intolerance.

3. Which type of lactose intolerance occurs due to an illness or injury?

  1. Primary lactose intolerance
  2. Secondary lactose intolerance
  3. Congenital lactose intolerance

Answer to Question #3

B is correct. Secondary lactose intolerance occurs due to injury, illness, or certain conditions like Crohn’s disease. Primary lactose intolerance develops during or after childhood, while congenital lactose intolerance is a rare condition where a baby cannot digest lactose from birth.

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