What is the Difference Between Lactose and Lactase

The main difference between lactose and lactase is that lactose is the disaccharide sugar, composed of galactose and glucose, whereas lactase is the enzyme produced in the liver to digest lactose.

In general, lactose and lactase are substrates and their specific enzyme, respectively. Lactose is the main reducing sugar that occurs in milk and milk products, which makes up 2-8% of the milk by mass. Lactase, on the other hand, is the enzyme that breaks down lactose into glucose and galactose. The lack of this enzyme in the body causes lactose intolerance.

Key Areas Covered

1. What is Lactose
   • Definition, Characteristics, Importance
2. What is Lactase
   • Definition, Characteristics, Importance
3. Similarities Between Lactose and Lactase
   • Outline of Common Features
4. Difference Between Lactose and Lactase
   • Comparison with Key Differences

Key Terms

Lactase, Lactose, Lactose Intolerance

What is Lactose

Lactose is the disaccharide sugar found in milk and milk products. Generally, the condensation of galactose and glucose makes up lactose. This forms a β-1→4 glycosidic linkage. Hence, the systematic name of lactose is β-D-galactopyranosyl-(1→4)-D-glucose. Here, glucose and galactose are major hexose sugars important in many metabolic reactions, including energy production.

Figure 1: Lactose

The dairy industry produces tons of lactose. Moreover, whey consists of 4/8% of lactose. When you consider the uses, lactase or β-D-galactopyranosyl-(1→4)-D-glucose is the enzyme responsible for the digestion of lactose inside the small intestine. In addition, digestion turns lactose into two simple sugars: glucose and galactose.

Moreover, lactose plays an important role in the absorption of calcium, copper, zinc, and phosphorus. Further to these, undigested lactose is used by intestinal microbiota. Lactose also promotes the growth of bifidobacteria in the gastrointestinal tract. Besides, lactose is one of the main sources of galactose, which plays a role in the development of the brain and nervous system.

However, it’s important to note that 65% of the human population cannot digest lactose due to the absence of the enzyme lactase. This condition is known as lactose intolerance. 

What is Lactase

Lactase is the enzyme responsible for the digestion of lactose. It is located in the brush border of the small intestine in humans and mammals. Importantly, the breaking down of the lactose into simple sugars gives the milk a sweetness. Moreover, lactose is a food supplement and is also used in the production of “lactose-free” milk.

Figure 2: Lactase Enzymatic Reaction

Furthermore, when the body does not produce enough lactase, one can experience the symptoms of lactose intolerance. Abdominal pain, bloating, diarrhea, flatulence, and nausea are the symptoms of lactose intolerance.

Similarities Between Lactose and Lactase

• Lactose and lactase refer to a substrate and its specific enzyme, respectively
• Moreover, lactose is the common disaccharide that occurs in milk and milk products, digested by the enzyme lactase into glucose and galactose in the small intestine. 

Difference Between Lactose and Lactase

Definition

Lactose is the disaccharide sugar occurring in milk and milk products, whereas lactase is the enzyme that digests lactose.

Type of Molecule

Lactose is a disaccharide while lactase is an enzyme.

Mode of Action

In addition, lactose is a sugar that occurs in milk and milk products while lactase digests lactose into glucose and galactose.

Conclusion

In brief, lactose is the disaccharide substrate of the enzyme lactase. Meanwhile, lactase is present in the small intestine and helps to digest lactose into glucose and galactose. One can feel the symptoms of lactose intolerance when one does not produce enough lactase enzymes inside the body. Therefore, the main difference between lactose and lactase is this relationship.

References:

1. NHS. (n.d.).”Causes–Lactose intolerance” Retrieved August 5, 2022.

Image Courtesy:

1. “Lactose Haworth” By NEUROtiker – Own Work (Public Domain) via Commons Wikimedia
2. “LactaseMechanism2” By Piccfa – Own Work (CC BY-SA 4.0) via Commons Wikimedia