What is the Difference Between LDH and Lactic Acid

The key difference between LDH and lactic acid is that LDH is an important enzyme in the cellular respiration process and catalyses the interconversion of lactate to pyruvate, while lactic acid is an organic acid that is produced when glucose is broken down to generate ATP in the absence of oxygen.

Anaerobic respiration in humans occurs during strenuous exercises when there is no sufficient oxygen supply. In this process, pyruvic acid, which is a by-product of glycolysis, is converted into lactic acid by LDH. This results in the build-up of lactic acid, leading to muscle fatigue. Therefore, LDH and lactic acid are two compounds that can be identified in the anaerobic respiration phase of cellular respiration.

1. Overview and Key Difference
2. What is LDH
3. What is Lactic Acid
4. Similarities – LDH and Lactic Acid
5. LDH vs Lactic Acid in Tabular Form
6. Summary – LDH vs Lactic Acid

What is LDH (Lactate Dehydrogenase)?

LDH (lactate dehydrogenase) is an important enzyme participating in the cellular respiration process. Here, it catalyses the interconversion of lactate to pyruvate. It also catalyses the concomitant inter-conversion of NAD⁺ to NADH. This enzyme converts the final product of glycolysis to lactic acid when oxygen is absent or in short supply. Moreover, it also catalyses the reverse reaction during the Cori cycle in the liver. This enzyme is found in all living cells. Generally, the dehydrogenase enzyme transfers a hydride from one molecule to another.

Figure 01: LDH

The active LDH consists of four main subunits. It also has five isoforms that are enzymatically similar but show different tissue distribution: LDH1 (heart and brain), LDH2 (reticuloendothelial system), LDH3 (lungs), LDH4 (kidney, placenta, and pancreas), LDH5 (liver, striated muscles, and brain). Moreover, a rare mutation in the genes controlling the production of lactate dehydrogenase leads to a medical condition known as LDH deficiency. Furthermore, on an LDH test or blood test, an elevated level of LDH usually indicates tissue damage, which has many potential causes like hemolytic anemia, vitamin B12 deficiency anemia, infarction, acute kidney disease, acute liver disease, pancreatitis, bone fractures, and cancers.

What is Lactic Acid?

Lactic acid is an organic acid that is produced when glucose is broken down to generate ATP in the absence of oxygen. Lactic acid was first discovered by the Swedish chemist Carl Wilhelm Scheele in 1780 from sour milk. It has the chemical formula of CH₃CH(OH)COOH. It is white in a solid state and a colorless solution in a dissolved state. Lactic acid is an alpha hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to a carboxyl group.

LDH and Lactic Acid - Side by Side Comparison

Figure 02: Lactic Acid

Anaerobic respiration in humans results in lactic acid production from pyruvic acid by the action of LDH during strenuous exercises when there is no sufficient oxygen supply. Moreover, lactic acid is produced industrially by bacterial fermentation of carbohydrates or by chemically from acetaldehyde. Furthermore, food manufacturers add lactic acids to food products such as bread, dessert, olives, and jams in order to give them long shelf life. In addition, it is specifically used to treat hyperpigmentation, age spots, and other factors that contribute to a dull and uneven skin complexion.

What are the Similarities Between LDH and Lactic Acid?

LDH and lactic acid are two compounds that can be identified in anaerobic respiration
Both compounds play a pivotal role in cellular respiration.
They can be identified in the human body.
Both compounds contribute to ATP production anaerobically.
They have different industrial uses.

What is the Difference Between LDH and Lactic Acid?

LDH is an important enzyme in the cellular respiration process, and it catalyses the interconversion of lactate to pyruvate, while lactic acid is an organic acid that is produced when glucose is broken down to generate ATP in the absence of oxygen. Thus, this is the key difference between LDH and lactic acid. Furthermore, the molecular weight of LDH is 144,000 g/mol, while the molecular weight of lactic acid is 90.08 g/mol.

The below infographic presents the differences between LDH and lactic acid in tabular form for side-by-side comparison.

Summary – LDH vs Lactic Acid

LDH and lactic acid are two compounds that can be identified in anaerobic respiration. In this process, pyruvic acid, which is a by-product of glycolysis, is converted into lactic acid by LDH. LDH is an important enzyme in cellular respiration. It catalyses the interconversion of lactate to pyruvate. L acid is an organic acid that is produced when glucose is broken down to generate ATP in the absence of oxygen. So, this summarizes the difference between LDH and lactic acid.

Reference:

1. “Lactate Dehydrogenase.” An Overview | ScienceDirect Topics.
2. Sayer, Amber. “What Is Lactic Acid?” LiveScience, Purch.

Image Courtesy:

1. “1i10” By Deposition authors: Read, J.A., Winter, V.J., Eszes, C.M., Sessions, R.B., Brady, R.L.; visualization author: User:Astrojan – RSCB (CC BY-SA 4.0) via Commons Wikimedia
2. “D-Lactic acid molecule ball” By Jynto (talk) – This image was created with Discovery Studio Visualizer. (CC0) via Commons Wikimedia