What is the Difference Between Lactic Acid and Lactate Dehydrogenase

The main difference between lactic acid and lactate dehydrogenase is that the L-lactate, the deprotonated form of lactic acid, is a byproduct of anaerobic glycolysis produced inside muscles during intense exercise while lactate dehydrogenase is the enzyme responsible for the interconversion of lactic acid and pyruvic acid

Lactic acid and lactate dehydrogenase are two forms of compounds to related metabolism under anaerobic conditions inside the body. Lactic acidosis is the accumulation of lactic acid in the bloodstream. Moreover, elevated levels of lactate dehydrogenase occur in various diseases including cardiac, renal, hepatic, and skeletal muscle diseases.

Key Areas Covered

1. What is Lactic Acid
     – Definition, Formation, Importance
2. What is Lactate Dehydrogenase
     – Definition, Types, Importance
3. What are the Similarities Between Lactic Acid and Lactate Dehydrogenase
     – Outline of Common features
4. What is the Difference Between Lactic Acid and Lactate Dehydrogenase
     – Comparison of Key Differences

Key Terms

Anaerobic Glycolysis, Lactate Dehydrogenase (LDH), Lactic Acid, Lactic Acidosis

Difference Between Lactic Acid and Lactate Dehydrogenase - Comparison Summary

What is Lactic Acid

Lactic acid is an organic compound, which is extremely soluble in water. Lactate is the conjugate of lactic acid and it is the deprotonated form of lactic acid. Lactate is produced inside the cells of the body under anaerobic conditions. Lactic acid fermentation is the process by which lactate is produced. It produces a small amount of ATP when compared to regular aerobic respiration. Here, pyruvate is the byproduct of aerobic glycolysis while lactate is the byproduct of anaerobic glycolysis. Therefore, lactic acid fermentation fuels muscles, delaying fatigue and prevent injury when oxygen delivery is severely limited in such conditions as intense exercise.

What is the Difference Between Lactic Acid and Lactate Dehydrogenase

Figure 1: Lactic Acid Fermentation

However, some pyruvates are also converted into lactate in response to the accumulation of NADH under oxygen deficiency. Nevertheless, cells release the excess lactic acid to the bloodstream. Therefore, the elevated levels of lactic acid in the bloodstream are an early indication of oxygen deprivation of hypoxia. The condition of elevated lactic acid in the blood is known as lactic acidosis. Type A lactic acidosis occurs due to the impairment of tissue oxygenation while Type B lactic acidosis occurs due to toxin-induced, impairments of cellular metabolism.

What is Lactate Dehydrogenase

Lactate dehydrogenase (LDH) is the enzyme responsible for the interconversion of lactic acid and pyruvate. It transfers hydrogen between the two compounds with the use of coenzyme NAD. This enzyme occurs in almost all the cells in the body. However, its activity is high in the liver, heart, skeletal muscles, kidney, and red blood cells. For instance, its activity is low in lungs, smooth muscles, and in the brain. Also, a number of disorders including heart failure, kidney, hepatic, and skeletal muscle disease can elevate the levels of lactate dehydrogenase in the blood.

Difference Between Lactic Acid and Lactate Dehydrogenase

Figure 2: Lactate Dehydrogenase Function

Furthermore, the five different forms of lactate dehydrogenase or the isoforms of the enzyme are LDH-1, LDH-2, LDH-3, LDH-4, and LDH-5. LDH-1 and LDH-2 are abundant in the heart and red blood cells; LDH-3 is common in lymph tissue, lungs, pancreas, and platelets; LDH-4 and liver and skeletal muscles are rich in LDH-5. The normal level of lactate dehydrogenase in the blood has to be 100-190 U/L in adults. However, genetic mutations result in low levels of lactate dehydrogenase in the body. Some individuals with low levels of this enzyme experience fatigue and muscle pain. Also, the consumption of high amounts of ascorbic acid may lower the levels of lactate dehydrogenase.

Similarities Between Lactic Acid and Lactate Dehydrogenase

  • Lactic acid and lactate dehydrogenase are two compounds related to the anaerobic glycolysis inside the body.
  • They are related to the conditions of the body when oxygen delivery is severely limited to a particular tissue of the body such as during intense exercise.
  • Also, both can occur in every type of cells in the body, but they more frequently occur in skeletal, heart, liver, kidney, and erythrocytes. They occur less frequently in the brain, smooth muscles, and in the lungs.

Difference Between Lactic Acid and Lactate Dehydrogenase

Definition

Lactic acid refers to a colorless syrupy organic acid formed in sour milk, and produced in the muscle tissues during strenuous exercise while lactate dehydrogenase refers to an enzyme important in the provision of muscle energy (carbohydrate metabolism), which is present in many cells, particularly those of the heart, kidneys, liver, and skeletal muscle. Thus, this is the fundaental difference between lactic acid and lactate dehydrogenase.

Significance

Furthermore, one main difference between lactic acid and lactate dehydrogenase is that the lactic acid is a byproduct of anaerobic glycolysis in tissues while lactate dehydrogenase is the enzyme responsible for the interconversion of lactic acid and pyruvate.

Reference Values

The normal level of lactic acid in the blood is 0.5-1 mmol/L while the normal level of lactate dehydrogenase in the blood is 100-190 U/L in adults.

Importance

The condition of having lactic acid in the bloodstream is known as lactic acidosis while the elevated levels of lactate dehydrogenase occur in various diseases including cardiac, renal, hepatic, and skeletal muscle diseases. Hence, this is also a difference between lactic acid and lactate dehydrogenase.

Conclusion

Lactic acid is the compound produced by the anaerobic glycolysis inside the body tissues body when oxygen delivery is severely limited. Lactate dehydrogenase is the enzyme responsible for the interconversion between lactic acid and pyruvate. It occurs in most of the body cells. However, the main difference between lactic acid and lactate dehydrogenase is their significance.

References:

1. Biggers, Alana. “Lactic Acidosis: What You Need to Know.” Healthline, Healthline Media, 1 Nov. 2018, Available Here.
2. Marcin, Judith. “Lactate Dehydrogenase Test.” Healthline, Healthline Media, 26 May 2017, Available Here.

Image Courtesy:

1. “Lactic acid fermentation” By Sjantoni – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “Lactate dehydrogenase mechanism” By Jazzlw – Own work (CC BY-SA 4.0) via Commons Wikimedia 

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things

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