The key difference between CRP and homocysteine is that the C reactive protein (CRP) is a pentameric protein while the homocysteine is a non-proteinogenic alpha amino acid.
Inflammation is a complex biological response developed against different harmful stimuli such as pathogens, damaged cells in the body, or irritants. It involves immune cells, molecular mediators and blood vessels. Moreover, different markers indicate possible inflammatory conditions. Hence, these markers are used at clinical levels to identify different disease conditions related to inflammation. C reactive protein (CRP) and homocysteine are two such markers.
CONTENTS
1. Overview and Key Difference
2. What is CRP
3. What is Homocysteine
4. Similarities Between CRP and Homocysteine
5. Side by Side Comparison – CRP vs Homocysteine in Tabular Form
6. Summary
What is CRP?
C Reactive Protein (CRP) is a pentameric protein present in blood plasma. It is a member of a pentraxins protein family with a monomer of 224 amino acids. The molecular mass of CRP is 25,106 Da. The gene that encodes CRP protein is present on chromosome 1. Furthermore, the CRP levels drastically rise in response to inflammation. Also, the CRP synthesis occurs in the liver in response to signalling factors released by macrophages and adipocytes during an inflammation.
Furthermore, CRP is an acute phase protein of hepatic origin. The increment in the level of CRP occurs due to the secretion of interleukin-6 by T lymphocytes and macrophages. Hence, the first pattern recognition receptor (PRR) identified during inflammation is the CRP.
Figure 01: CRP
Besides, the physiological role of CRP involves binding to lysophosphatidylcholine, which is present on the surface of dying or dead cells. Once bound, it activates the complement pathway via complement component 1q(C1q). Hence, this promotes phagocytosis by macrophages and clears apoptotic cells, necrotic cells, and bacteria.
What is Homocysteine?
Homocysteine is a non-proteinogenic alpha amino acid, which is a homologue of cysteine amino acid with an additional methylene bridge. The body cannot obtain homocysteine from the diet. Therefore, biosynthesis of homocysteine occurs by a multi-step process from methionine with the removal of the terminal carbon methyl group. Through B vitamins, homocysteine has the potential to convert back to methionine or cysteine depending on the need.
Besides, abnormal levels of homocysteine cause various disease conditions. Increment from the normal level of homocysteine causes hyperhomocysteinemia. And, this disease condition results in endothelial cell injury. It leads to blood vessel inflammation and converts to atherogenesis. Finally, it causes ischemic injury (restriction in the supply of blood to tissues). Therefore, hyperhomocysteinemia act as a possible risk for coronary heart disease. It occurs due to blocking of blood flow to the coronary arteries by an atherosclerotic plaque. Thus, this limits the supply of oxygenated blood to the heart.
Figure 02: Homocysteine
There is a correlation between hyperhomocysteinemia and the occurrence of strokes, heart attacks, and blood clots. But, it is still unclear whether hyperhomocysteinemia is an independent risk factor for such disease conditions. Also, early pregnancy loss and neural tube defects could occur due to hyperhomocysteinemia.
What are the Similarities Between CRP and Homocysteine?
- CRP and Homocysteine are markers of inflammation.
- High levels of both types indicate disease conditions.
- Also, they both are present in the blood.
- Both can be measured at clinical levels.
- Furthermore, they are reliable clinical indicators of inflammation and other disease types.
What is the Difference Between CRP and Homocysteine?
CRP is a protein while homocysteine is a non-proteinogenic amino acid. Therefore, this is the key difference between CRP and homocysteine. Furthermore, CRP synthesis occurs in the liver while homocysteine biosynthesis occurs from methionine through a metabolic pathway. Hence, this is also a difference between CRP and homocysteine.
The below infographic on the difference between CRP and homocysteine provides a more detailed comparison.
Summary – CRP vs Homocysteine
Different markers indicate inflammatory reaction conditions in our body. Among the many different markers, C reactive protein and homocysteine are two important inflammatory markers. CRP is a pentameric protein present in blood plasma whose level rises due to inflammation. Accordingly, the liver is the organ that synthesizes CRP in response to signalling factors released by macrophages and adipocytes.
On the other hand, homocysteine is a non-proteinogenic alpha amino acid, which is a homologue of amino acid cysteine with an additional methylene bridge. Hence, the increment from the normal level of homocysteine causes hyperhomocysteinemia that causes ischemic injury. Moreover, hyperhomocysteinemia acts as a possible risk for coronary heart disease as well. Thus, this is the difference between CRP and homocysteine.
Reference:
1.”Homocysteine.”. “Homocysteine.” The Columbia Encyclopedia, 6th Ed, Encyclopedia.com, 2018. Available here
2.Protein.”, “C-Reactive. “C-Reactive Protein.” The Columbia Encyclopedia, 6th Ed, Encyclopedia.com, 2018. Available here
Image Courtesy:
1.”PDB 1b09 EBI”By Jawahar Swaminathan and MSD staff at the European Bioinformatics Institute (Public Domain) via Commons Wikimedia
2.”L-Homocysteine-3D-balls”By Ben Mills and Jynto (Public Domain) via Commons Wikimedia