Blood protein

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Blood-proteins, also termed plasma proteins, are proteins present in blood plasma. They serve many different functions, including transport of lipids, hormones, vitamins and minerals in activity and functioning of the immune system. Other blood proteins act as enzymes, 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.

Contents

Serum albumin accounts for 55% of blood proteins, [1] 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. The remainder of the plasma proteins (1%) are regulatory proteins, such as enzymes, proenzymes, and hormones. All blood proteins are synthesized in liver except for the gamma globulins. [1]

Families of blood proteins

Blood proteinNormal level %Function
Albumins 3.5-5.0 g/dl55%create and maintain osmotic pressure; transport insoluble molecules
Globulins 2.0-2.5 g/dl38%participate in immune system
Fibrinogen 0.2-0.45 g/dl7%Blood coagulation
Regulatory proteins <1%Regulation of gene expression
Clotting factors <1%Conversion of fibrinogen into fibrin

Examples of specific blood proteins:

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 [2] efforts in the 1970s, and in more recent times this research has been performed using LC-tandem MS [3] [4] 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. [5]

Related Research Articles

<span class="mw-page-title-main">Clinical chemistry</span> Area of clinical pathology that is generally concerned with analysis of bodily fluids

Clinical chemistry is a division in medical laboratory sciences focusing on qualitative tests of important compounds, referred to as analytes or markers, in bodily fluids and tissues using analytical techniques and specialized instruments. This interdisciplinary field includes knowledge from medicine, biology, chemistry, biomedical engineering, informatics, and an applied form of biochemistry.

<span class="mw-page-title-main">Lipoprotein</span> Biochemical assembly whose purpose is to transport hydrophobic lipid molecules

A lipoprotein is a biochemical assembly whose primary function is to transport hydrophobic lipid molecules in water, as in blood plasma or other extracellular fluids. They consist of a triglyceride and cholesterol center, surrounded by a phospholipid outer shell, with the hydrophilic portions oriented outward toward the surrounding water and lipophilic portions oriented inward toward the lipid center. A special kind of protein, called apolipoprotein, is embedded in the outer shell, both stabilising the complex and giving it a functional identity that determines its role.

<span class="mw-page-title-main">Blood plasma</span> Liquid component of blood

Blood plasma is a light amber-colored liquid component of blood in which blood cells are absent, but which contains proteins and other constituents of whole blood in suspension. It makes up about 55% of the body's total blood volume. It is the intravascular part of extracellular fluid. It is mostly water, and contains important dissolved proteins, glucose, clotting factors, electrolytes, hormones, carbon dioxide, and oxygen. It plays a vital role in an intravascular osmotic effect that keeps electrolyte concentration balanced and protects the body from infection and other blood-related disorders.

<span class="mw-page-title-main">Serum protein electrophoresis</span> Laboratory test

Serum protein electrophoresis is a laboratory test that examines specific proteins in the blood called globulins. The most common indications for a serum protein electrophoresis test are to diagnose or monitor multiple myeloma, a monoclonal gammopathy of uncertain significance (MGUS), or further investigate a discrepancy between a low albumin and a relatively high total protein. Unexplained bone pain, anemia, proteinuria, chronic kidney disease, and hypercalcemia are also signs of multiple myeloma, and indications for SPE. Blood must first be collected, usually into an airtight vial or syringe. Electrophoresis is a laboratory technique in which the blood serum is applied to either an acetate membrane soaked in a liquid buffer, or to a buffered agarose gel matrix, or into liquid in a capillary tube, and exposed to an electric current to separate the serum protein components into five major fractions by size and electrical charge: serum albumin, alpha-1 globulins, alpha-2 globulins, beta 1 and 2 globulins, and gamma globulins.

<span class="mw-page-title-main">Serum (blood)</span> Fluid and solute component of blood

Serum is the fluid and solute component of blood which does not play a role in clotting. It may be defined as blood plasma without the clotting factors, or as blood with all cells and clotting factors removed. Serum includes all proteins not used in blood clotting; all electrolytes, antibodies, antigens, hormones; and any exogenous substances. Serum does not contain white blood cells (leukocytes), red blood cells (erythrocytes), platelets, or clotting factors.

<span class="mw-page-title-main">Alpha-1 antitrypsin</span> Mammalian protein found in Homo sapiens

Alpha-1 antitrypsin or α1-antitrypsin is a protein belonging to the serpin superfamily. It is encoded in humans by the SERPINA1 gene. A protease inhibitor, it is also known as alpha1–proteinase inhibitor (A1PI) or alpha1-antiproteinase (A1AP) because it inhibits various proteases. In older biomedical literature it was sometimes called serum trypsin inhibitor, because its capability as a trypsin inhibitor was a salient feature of its early study. As a type of enzyme inhibitor, it protects tissues from enzymes of inflammatory cells, especially neutrophil elastase, and has a reference range in blood of 0.9–2.3 g/L, but the concentration can rise manyfold upon acute inflammation.

The globulins are a family of globular proteins that have higher molecular weights than albumins and are insoluble in pure water but dissolve in dilute salt solutions. Some globulins are produced in the liver, while others are made by the immune system. Globulins, albumins, and fibrinogen are the major blood proteins. The normal concentration of globulins in human blood is about 2.6-3.5 g/dL.

<span class="mw-page-title-main">Transcortin</span> Protein found in humans

Transcortin, also known as corticosteroid-binding globulin (CBG) or serpin A6, is a protein produced in the liver in animals. In humans it is encoded by the SERPINA6 gene. It is an alpha-globulin.

<span class="mw-page-title-main">Acute-phase protein</span> Class of proteins involved in inflammation

Acute-phase proteins (APPs) are a class of proteins whose concentrations in blood plasma either increase or decrease in response to inflammation. This response is called the acute-phase reaction. The acute-phase reaction characteristically involves fever, acceleration of peripheral leukocytes, circulating neutrophils and their precursors. The terms acute-phase protein and acute-phase reactant (APR) are often used synonymously, although some APRs are polypeptides rather than proteins.

<span class="mw-page-title-main">Serum albumin</span> Type of globular protein produced by the liver

Serum albumin, often referred to simply as blood albumin, is an albumin found in vertebrate blood. Human serum albumin is encoded by the ALB gene. Other mammalian forms, such as bovine serum albumin, are chemically similar.

<span class="mw-page-title-main">Sex hormone-binding globulin</span> Human glycoprotein that binds to androgens and estrogens

Sex hormone-binding globulin (SHBG) or sex steroid-binding globulin (SSBG) is a glycoprotein that binds to androgens and estrogens. When produced by the Sertoli cells in the seminiferous tubules of the testis, it is called androgen-binding protein (ABP).

<span class="mw-page-title-main">Monoclonal gammopathy</span> Excess myeloma protein or monoclonal gamma globulin in the blood

Monoclonal gammopathy, also known as paraproteinemia, is the presence of excessive amounts of myeloma protein or monoclonal gamma globulin in the blood. It is usually due to an underlying immunoproliferative disorder or hematologic neoplasms, especially multiple myeloma. It is sometimes considered equivalent to plasma cell dyscrasia. The most common form of the disease is monoclonal gammopathy of undetermined significance.

<span class="mw-page-title-main">Hypoalbuminemia</span> Medical condition

Hypoalbuminemia is a medical sign in which the level of albumin in the blood is low. This can be due to decreased production in the liver, increased loss in the gastrointestinal tract or kidneys, increased use in the body, or abnormal distribution between body compartments. Patients often present with hypoalbuminemia as a result of another disease process such as malnutrition as a result of severe anorexia nervosa, sepsis, cirrhosis in the liver, nephrotic syndrome in the kidneys, or protein-losing enteropathy in the gastrointestinal tract. One of the roles of albumin is being the major driver of oncotic pressure in the bloodstream and the body. Thus, hypoalbuminemia leads to abnormal distributions of fluids within the body and its compartments. As a result, associated symptoms include edema in the lower legs, ascites in the abdomen, and effusions around internal organs. Laboratory tests aimed at assessing liver function diagnose hypoalbuminemia. Once identified, it is a poor prognostic indicator for patients with a variety of different diseases. Yet, it is only treated in very specific indications in patients with cirrhosis and nephrotic syndrome. Treatment instead focuses on the underlying cause of the hypoalbuminemia. Albumin is an acute negative phase respondent and not a reliable indicator of nutrition status.

<span class="mw-page-title-main">Human serum albumin</span> Albumin found in human blood

Human serum albumin is the serum albumin found in human blood. It is the most abundant protein in human blood plasma; it constitutes about half of serum protein. It is produced in the liver. It is soluble in water, and it is monomeric.

<span class="mw-page-title-main">Albumin</span> Family of globular proteins

Albumin is a family of globular proteins, the most common of which are the serum albumins. All of the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins are commonly found in blood plasma and differ from other blood proteins in that they are not glycosylated. Substances containing albumins are called albuminoids.

The Cohn process, developed by Edwin J. Cohn, is a series of purification steps with the purpose of extracting albumin from blood plasma. The process is based on the differential solubility of albumin and other plasma proteins based on pH, ethanol concentration, temperature, ionic strength, and protein concentration. Albumin has the highest solubility and lowest isoelectric point of all the major plasma proteins. This makes it the final product to be precipitated, or separated from its solution in a solid form. Albumin was an excellent substitute for human plasma in World War Two. When administered to wounded soldiers or other patients with blood loss, it helped expand the volume of blood and led to speedier recovery. Cohn's method was gentle enough that isolated albumin protein retained its biological activity.

<span class="mw-page-title-main">Protein C inhibitor</span> Human protein

Protein C inhibitor is a serine protease inhibitor (serpin) that limits the activity of protein C.

<span class="mw-page-title-main">Vitamin D-binding protein</span> Mammalian protein found in Homo sapiens

Vitamin D-binding protein (DBP), also/originally known as gc-globulin, is a protein that in humans is encoded by the GC gene. DBP is genetically the oldest member of the albuminoid family and appeared early in the evolution of vertebrates.

Blood plasma fractionation are the general processes separating the various components of blood plasma, which in turn is a component of blood obtained through blood fractionation. Plasma-derived immunoglobulins are giving a new narrative to healthcare across a wide range of autoimmune inflammatory diseases. This widespread applicability is anticipated to leverage market prospects for plasma fractionation, pegged to witness a noteworthy 7% CAGR. COVID-19 pandemic is expected to generate growth opportunities for the plasma fractionation market.

The liver plays the major role in producing proteins that are secreted into the blood, including major plasma proteins, factors in hemostasis and fibrinolysis, carrier proteins, hormones, prohormones and apolipoprotein:

References

  1. 1 2 Smith, Graham S.; Walter, Gail L.; Walker, Robin M. (2013-01-01), Haschek, Wanda M.; Rousseaux, Colin G.; Wallig, Matthew A. (eds.), "Chapter 18 - Clinical Pathology in Non-Clinical Toxicology Testing", Haschek and Rousseaux's Handbook of Toxicologic Pathology (Third Edition), Boston: Academic Press, pp. 565–594, doi:10.1016/b978-0-12-415759-0.00018-2, ISBN   978-0-12-415759-0 , retrieved 2020-11-16
  2. Anderson NL, Anderson NG (1977). "High Resolution Two-Dimensional Electrophoresis of Human Plasma Proteins". Proceedings of the National Academy of Sciences. 74 (12): 5421–5425. Bibcode:1977PNAS...74.5421A. doi: 10.1073/pnas.74.12.5421 . PMC   431746 . PMID   271964.
  3. Adkins JN; et al. (2002). "Toward a human blood serum proteome: analysis by multidimensional separation coupled with mass spectrometry". Molecular & Cellular Proteomics. 1 (12): 947–955. doi: 10.1074/mcp.M200066-MCP200 . PMID   12543931.
  4. Malmström, E; Kilsgård, O; Hauri, S; Smeds, E; Herwald, H; Malmström, L; Malmström, J (January 2016). "Large-scale inference of protein tissue origin in gram-positive sepsis plasma using quantitative targeted proteomics". Nat Commun. 7: 10261. Bibcode:2016NatCo...710261M. doi:10.1038/ncomms10261. PMC   4729823 . PMID   26732734.
  5. Geyer, PE; Kulak, NA; Pichler, G; Holdt, LM; Teupser, D; Mann, M; Chuang (November 2013). "Photoaffinity labeling of plasma proteins". Molecules. 18 (11): 13831–13859. doi: 10.3390/molecules181113831 . PMC   6270137 . PMID   24217326.