Lactase

the characteristic sugar of milk; in more technical terms, this protein is responsible for the enzymatic hydrolysis of lactose into glucose and galactose:

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lactose + H2O → galactose + glucose

Lactose is a sugar, a typical disaccharide of milk and its derivatives. In one hundred grams of cow's milk we find about 5 grams, while in breast milk the percentage content is close to 7% by weight.

, which as it is known cover the intestinal villi increasing the absorbent surface. In this same site there are other disaccharidases, proteins with an enzymatic action similar to that of lactase responsible for the digestion of disaccharides such as sucrose (normal cooking sugar) and maltose.

The optimal conditions for lactase activity are obtained at temperatures of 48 ° C and at pH close to neutrality.

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Lactase belongs to the group of β-galactosidases, a family of hydrolytic enzymes which in the presence of water catalyze the cleavage of β-galactosides in the monomers that constitute them (β-galactoside is defined as a simple compound with a sugar part consisting of galactose, bound to "another molecule through a glycosidic bond that is" below "the plane of the galactose molecule).

, flatulence and diarrhea following the ingestion of milk and foods rich in lactose.

Causes of lactose intolerance

Congenital lactase deficiency is quite rare and transmitted with autosomal recessive inheritance; it manifests itself from the first days of life with watery diarrhea, abdominal cramps, flatulence and abdominal distension; obviously the problem occurs with both infant formula and mother's milk and can only be solved by resorting to delactosed or vegetable milks (such as rice or soy).

With growth, starting from 3-5 years, there is a progressive reduction in the activity of lactase, up to 90-95%. In adulthood, the digestive capacity of lactose can remain at high, medium levels or drop significantly to the point of unleashing an "acquired intolerance. The residual activity conditions the maximum quantity of lactose that can be consumed without suffering from the aforementioned gastrointestinal disorders. In this regard, there are significant differences in the population resulting from polymorphisms of the gene that codes for the enzyme.

Temporary deficits in lactase activity also occur as a result of diseases or conditions that damage the intestinal mucosa, such as viral gastroenteritis and celiac disease. The fact of not drinking milk for very long periods can also make the body "forget" how to produce the enzyme, and vice versa; to summarize it is said that lactase is an inducible enzyme.

Lactase and Evolution

Adult hypolactasia is believed to be a primitive condition, later modified by the introduction of agriculture and pastoralism in the Neolithic period. Not surprisingly, the persistence of lactase in adulthood (considered in this sense the "real" anomaly) is typical of the geographic areas where pastoralism has developed (such as Northern Europe); on the contrary, there is a "high incidence of lactose intolerance in Southeast Asia and South Africa, areas where milk consumption is traditionally low or absent.