plasma proteins

Blood proteins

Blood proteins, also called serum proteins, are proteins found in blood plasma. Serum total protein in blood is 7g/dl, which in total makes 7% of total body weight. 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:

Blood protein Normal level % Function
Albumins 3.5-5.0 g/dl 60% create osmotic pressure and transports other molecules
immunoglobulins 1.0-1.5 g/dl 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)

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 and this 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 efforts in the 1970s and in more recent times this research has been performed using LC-tandem MS based proteomics.


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

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