Plasma proteins, sometimes referred to as blood proteins, are

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s present in blood plasma. They perform many different functions, including transport of

hormone A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physio ...

vitamin Vitamins are Organic compound, organic molecules (or a set of closely related molecules called vitamer, vitamers) that are essential to an organism in small quantities for proper metabolism, metabolic function. Nutrient#Essential nutrients, ...

s and

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s in activity and functioning of the

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

. Other blood proteins act as

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s, complement, components, protease inhibitors or kinin precursors. Contrary to popular belief, haemoglobin is not a blood protein, as it is carried within red blood cells, rather than in the blood serum.

Serum albumin Serum albumin, often referred to simply as blood albumin, is an albumin (a type of globular protein) found in vertebrate blood. Human serum albumin is encoded by the ''ALB'' gene. Other mammalian forms, such as bovine serum albumin, are chem ...

accounts for 55% of blood proteins, is a major contributor to maintaining the oncotic pressure of plasma and assists, as a carrier, in the transport of lipids and steroid hormones. Globulins make up 38% of blood proteins and transport ions, hormones, and lipids assisting in immune function. Fibrinogen comprises 7% of blood proteins; conversion of fibrinogen to insoluble fibrin is essential for

blood clotting Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a thrombus, blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of co ...

. The remainder of the plasma proteins (1%) are regulatory proteins, such as enzymes, proenzymes, and

hormones A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physiology and behavior. Hormones a ...

. All blood proteins are synthesized in

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

except for the gamma globulins.

Families of blood proteins

Examples of specific blood proteins: * Prealbumin ( transthyretin) * Alpha 1 antitrypsin (neutralizes trypsin that has leaked from the

digestive system The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...

) * Alpha-1-acid glycoprotein * Alpha-1-fetoprotein * alpha2-macroglobulin * Gamma globulins * Beta-2 microglobulin * Haptoglobin * Human Serum Albumin * Ceruloplasmin *

Complement component 3 Complement may refer to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-class collections into complementary sets * Complementary color, in the vi ...

* Complement component 4 * C-reactive protein (CRP) * Lipoproteins (chylomicrons, VLDL, LDL, HDL) *

Transferrin Transferrins are glycoproteins found in vertebrates which bind and consequently mediate the transport of iron (Fe) through blood plasma. They are produced in the liver and contain binding sites for two Iron(III), Fe3+ ions. Human transferrin is ...

* Prothrombin * MBL or MBP

Clinical significance

Separating serum proteins by electrophoresis is a valuable diagnostic tool, as well as a way to monitor clinical progress. 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. The normal laboratory value of serum total protein is around 7 g/dL. Scientists are able to identify blood proteins using Photo-affinity labeling, a means of using photo-reactive ligands as a labeling agent to identify targeted proteins.

References

* Clinical Chemistry : a laboratory perspective / dited byWendy Arneson, Jean Brickell. {{Authority control Blood proteins