What is the Difference Between Salvage Pathway and De Novo Synthesis

The main difference between salvage pathway and de novo synthesis is that the salvage pathway is more energy efficient whereas De novo pathway is less energy efficient.

The salvage pathway and de novo pathway are two types of nucleotide synthesis pathways involving the biosynthesis of purines and pyrimidine nucleotides. Generally, the salvage pathway occurs through preformed purine and pyrimidine bases, while de novo synthesis occurs through small molecules.            

Key Areas Covered

1. What is Salvage Pathway
     – Definition, Features, Importance
2. What is De Novo Synthesis
     – Definition, Features, Importance
3. Similarities Between Salvage Pathway and De Novo Synthesis
     – Outline of Common Features
4. Difference Between Salvage Pathway and De Novo Synthesis
     – Comparison of Key Differences

Key Terms                                                                                                                  

De Novo Synthesis, Salvage Pathway

What is Salvage Pathway

The salvage pathway is the synthesis of biological products from intermediates produced by the degradation pathway or similar molecules. Therefore, the nucleotide salvage pathway is responsible for the biosynthesis of nucleotides; in other words, purines and pyrimidines form the intermediates of the degradation pathway. Generally, the degradation of DNA and RNA produces bases and nucleosides. Therefore, the main function of the salvage pathway of nucleotides is to recover and reuse the above-mentioned bases and nucleosides.

Figure 1: Salvage Pathway of Pyrimidine

Furthermore, the salvage pathway is important in some tissues in which the other pathways of nucleotide synthesis cannot occur. In addition to that, the salvage pathway is important as a target for drug development. Normally, the salvage pathway is useful as a treatment for a number of diseases in humans in purine a pyrimidine metabolism. However, purine and pyrimidine salvage pathways occur through the bases or nucleosides of purines and pyrimidines. Other biomolecules, such as methionine and nicotinate, also have their own salvage pathways.   

What is De Novo Synthesis

De novo synthesis is the biosynthesis of complex molecules starting from small molecules such as sugars and amino acids. Therefore, nucleotides can be synthesized from small precursor molecules such as aspartate and formate. However, some molecules, such as methionine, cannot be synthesized from the de novo pathway. Hence, these molecules should be taken from the diet. In purine de novo synthesis, the synthesis of a purine ring occurs by one atom or a few atoms at one time attached to the ribose. On the other hand, in pyrimidine de novo biosynthesis, orotate is the initial molecule in the synthesis of the pyrimidine ring. First, orotate attaches to the ribose, and then synthesis of pyrimidine nucleotide can occur.

Figure 2: Do Novo Synthesis of GMP

Moreover, in de novo synthesis, cholesterol serves as the precursor molecule to the biosynthesis of bile acid, steroid hormones, and vitamin D. In mammals, cholesterol is either synthesized in the body through de novo synthesis or it comes through the diet.   

Similarities Between Salvage Pathway and De Novo Synthesis

• Salvage and de novo synthesis are two types of nucleotide synthesis pathways.
• Both synthesize purines and pyrimidines from different types of molecules.

Difference Between Salvage Pathway and De Novo Synthesis

Definition

The salvage pathway refers to a pathway in which a biological product is produced from intermediates in the degradative pathway of its own or a similar substance, while de novo synthesis refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids.

Occurrence

The salvage pathway occurs through preformed purine and pyrimidine bases, while de novo synthesis starts through small molecules.

Efficiency

While the salvage pathway is more energy efficient, the de novo pathway is less energy efficient.

Conclusion                                                      

In brief, the salvage pathway and de novo pathway are two types of nucleotide biosynthesis pathways. Generally, the main function of both pathways is to synthesize purines and pyrimidines. The salvage pathway occurs from the preformed purine and pyrimidine bases. This pathway is more energy efficient. In comparison, de novo synthesis begins through small molecules. In addition, the de novo pathway is comparatively less energy efficient. Therefore, the main difference between salvage pathway and de novo pathway is the type of biosynthesis.

References:                

1. Nucleotide Synthesis via Salvage Pathway, William L Nyhan (n.d.). Wiley Online Library Retrieved April 4, 2023.

Image Courtesy:

1. “GMP de novo synthesis” By Pierpaolo.cordone – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Pyrimidine Ribonucleotide Salvage” By Crenim – Own Work (CC0) via Commons Wikimedia