Blood Plasma Proteins / Serum Proteins

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Blood proteins, also called serum proteins, are proteins found in blood plasma. Serum total protein in blood is 7g/dl. They serve many different functions, including

• circulatory transport molecules for lipids, hormones, vitamins and metals
• enzymes, complement components, protease inhibitors, and kinin precursors
• regulation of acellular activity and functioning and in the immune system.

Separating serum proteins by electrophoresis is a valuable diagnostic tool as well as a way to monitor clinical progress.

Often mentioned blood proteins:

 

 

 

Structure of Hemoglobin

 

 

 

Blood protein	Normal level	%	Function
Albumins	3.5-5.0 g/dl	60%	create oncotic pressure and transports other molecules
immunoglobulins	1.0-1.5 g/dl	18%	participate in immune system
Fibrinogens	0.2-0.45 g/dl	4%	blood coagulation
alpha 1-antitrypsin			neutralize trypsin that has leaked from the digestive system
Regulatory proteins		<1%	Regulation of gene ｅxpression

Other types of blood proteins include: Prealbumin Alpha 1 antitrypsin Alpha 1 acid glycoprotein Alpha 1 fetoprotein Haptoglobin Alpha 2 macroglobulin Ceruloplasmin Transferring C3/C4 Beta 2 microglobulin Beta lipoprotein Gamma globulin proteins C-reactive protein (CRP)

• alpha2-macroglobulin
• Other globulins, which are of three types- alpha, beta and gamma.
• Lipoproteins (chylomicrons, VLDL, LDL, HDL)
• Transferrin
• Prothrombin

All the plasma proteins are synthesized in liver except gamma globulins.

60% of plasma proteins are made up of the protein albumin, which are major contributors to osmotic pressure of plasma which assists in the transport of lipids and steroid hormones. Globulins make up 35% of plasma proteins and are used in the transport of ions, hormones and lipids assisting in immune function. 4% is fibrinogen which is essential in the clotting of blood and can be converted into insoluble fibrin. Regulatory proteins which make up less than 1% of plasma proteins are proteins such as enzymes, proenzymes and hormones. Current research regarding blood plasma proteins is centered on performing proteomics analyses of serum/plasma in the search for biomarkers. These efforts started with two-dimensional gel electrophoresis^[1] efforts in the 1970s and in more recent times this research has been performed using LC-tandem MS^[2][3] based proteomics.

References

1. ^ Anderson NL and Anderson NG (1977). "High Resolution Two-Dimensional Electrophoresis of Human Plasma Proteins". Proceeding of the National Academy of Sciences 74 (12): 5421–5425. doi:10.1073/pnas.74.12.5421. PMID 271964. 
2. ^ Adkins JN et al. (2002). "Toward a human blood serum proteome: analysis by multidimensional separation coupled with mass spectrometry". Molecular and Cellular Proteomics 1 (12): 947–955. doi:10.1074/mcp.M200066-MCP200. PMID 12543931. 
3. ^ Jacobs JM et al. (2005). "Utilizing human blood plasma for proteomic biomarker discovery". Journal of Proteome Research 4 (4): 1073–1085. doi:10.1021/pr0500657. PMID 16083256. 

Clinical Chemistry : a laboratory perspective / [edited by] Wendy Arneson, Jean Brickell.