Proteins produced and secreted by the liver
Encyclopedia
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 apolipoproteins:
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
plays the major role in producing proteins that are secreted
Secretion
Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland. In contrast to excretion, the substance may have a certain function, rather than being a waste product...
into the blood, including major plasma proteins, factors in hemostasis
Hemostasis
Hemostasis or haemostasis is a process which causes bleeding to stop, meaning to keep blood within a damaged blood vessel . Most of the time this includes blood changing from a liquid to a solid state. Intact blood vessels are central to moderating blood's tendency to clot...
and fibrinolysis
Fibrinolysis
Fibrinolysis is a process that prevents blood clots from growing and becoming problematic. This process has two types: primary fibrinolysis and secondary fibrinolysis...
, carrier proteins, hormones, prohormones and apolipoproteins:
Major plasma proteins
- Human serum albuminHuman serum albuminHuman serum albumin is the most abundant protein in human blood plasma. It is produced in the liver. Albumin constitutes about half of the blood serum protein...
, osmolyteOsmolyteOsmolytes are compounds affecting osmosis. They are soluble in the solution within a cell, or in the surrounding fluid, e.g. as plasma osmolytes. They play a role in maintaining cell volume and fluid balance. For example, when a cell swells due to external osmotic pressure, membrane channels open...
and carrier proteinCarrier proteinCarrier proteins are proteins involved in the movement of ions, small molecules, or macromolecules, such as another protein, across a biological membrane. Carrier proteins are integral membrane proteins; that is they exist within and span the membrane across which they transport substances. The... - α-fetoprotein, the fetal counterpart of serum albumin
- Soluble plasma fibronectinFibronectinFibronectin is a high-molecular weight glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins. In addition to integrins, fibronectin also binds extracellular matrix components such as collagen, fibrin and heparan sulfate proteoglycans...
, forming a blood clot that stops bleeding - C-reactive proteinC-reactive proteinC-reactive protein is a protein found in the blood, the levels of which rise in response to inflammation...
, opsoninOpsoninAn opsonin is any molecule that targets an antigen for an immune response. However, the term is usually used in reference to molecules that act as a binding enhancer for the process of phagocytosis, especially antibodies, which coat the negatively-charged molecules on the membrane. Molecules that...
on microbes , acute phase proteinAcute phase proteinAcute-phase proteins are a class of proteins whose plasma concentrations increase or decrease in response to inflammation... - Various other globulins
Factors in hemostasis and fibrinolysis
- Stimulators of coagulation:
- All factors in the coagulation cascade, except factor VIIIFactor VIIIFactor VIII is an essential blood clotting factor also known as anti-hemophilic factor . In humans, Factor VIII is encoded by the F8 gene...
(from endothelium)
- All factors in the coagulation cascade, except factor VIII
- Inhibitors of coagulation:, inactivate an enormous variety of proteinases
- α2-macroglobulin
- α1-antitrypsin
- Antithrombin III
- Protein SProtein SProtein S is a vitamin K-dependent plasma glycoprotein synthesized in the endothelium. In the circulation, Protein S exists in two forms: a free form and a complex form bound to complement protein C4b. In humans, protein S is encoded by the PROS1 gene...
- Protein CProtein CProtein C, also known as autoprothrombin IIA and blood coagulation factor XIV, is a zymogenic protein, the activated form of which plays an important role in regulating blood clotting, inflammation, cell death and maintaining the permeability of blood vessel walls in humans and other animals...
- Fibrinolysis:, breakdown of fibrinFibrinFibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....
clots- plasminogen
- Inhibitors of fibrinolysis
- α2-antiplasmin
- Complement components C1-9, Complement component 3 (C3)
Carrier proteins
- AlbuminAlbuminAlbumin refers generally to any protein that is water soluble, which is moderately soluble in concentrated salt solutions, and experiences heat denaturation. They are commonly found in blood plasma, and are unique to other blood proteins in that they are not glycosylated...
, carries thyroid hormoneThyroid hormoneThe thyroid hormones, thyroxine and triiodothyronine , are tyrosine-based hormones produced by the thyroid gland primarily responsible for regulation of metabolism. An important component in the synthesis of thyroid hormones is iodine. The major form of thyroid hormone in the blood is thyroxine ,...
s and other hormones, particularly fat soluble ones, fatty acids to the liver, unconjugated bilirubinBilirubinBilirubin is the yellow breakdown product of normal heme catabolism. Heme is found in hemoglobin, a principal component of red blood cells. Bilirubin is excreted in bile and urine, and elevated levels may indicate certain diseases...
, many drugsMedicationA pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
and Ca2+CalciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust... - CeruloplasminCeruloplasminCeruloplasmin is a ferroxidase enzyme that in humans is encoded by the CP gene.Ceruloplasmin is the major copper-carrying protein in the blood, and in addition plays a role in iron metabolism. It was first described in 1948...
, carries copperCopperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish... - TranscortinTranscortinTranscortin, also corticosteroid-binding globulin or CBG, is officially called serpin peptidase inhibitor, clade A , member 6.It is an alpha-globulin.-Binding:...
, carries cortisolCortisolCortisol is a steroid hormone, more specifically a glucocorticoid, produced by the adrenal gland. It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat,...
, aldosteroneAldosteroneAldosterone is a hormone that increases the reabsorption of sodium ions and water and the release of potassium in the collecting ducts and distal convoluted tubule of the kidneys' functional unit, the nephron. This increases blood volume and, therefore, increases blood pressure. Drugs that...
and progesteroneProgesteroneProgesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species... - HaptoglobinHaptoglobinHaptoglobin is a protein that in humans is encoded by the HP gene. In blood plasma, haptoglobin binds free hemoglobin released from erythrocytes with high affinity and thereby inhibits its oxidative activity. The haptoglobin-hemoglobin complex will then be removed by the reticuloendothelial system...
, carries free hemoglobin released from erythrocytes - Hemopexin, carries free heme released from hemoglobin
- IGF binding proteinInsulin-like growth factor binding proteinThe Insulin-like growth factor-binding protein also known as IGFBP serves as a carrier protein for Insulin-like growth factor 1 .- Function :...
, carries insulin-like growth factor 1Insulin-like growth factor 1Insulin-like growth factor 1 also known as somatomedin C is a protein that in humans is encoded by the IGF1 gene. IGF-1 has also been referred to as a "sulfation factor" and its effects were termed "nonsuppressible insulin-like activity" in the 1970s.IGF-1 is a hormone similar in molecular... - Major urinary proteinsMajor urinary proteinsMajor urinary proteins , also known as α2u-globulins, are a subfamily of proteins found in abundance in the urine and other secretions of many animals. Mups provide a small range of identifying information about the donor animal, when detected by the vomeronasal organ of the receiving animal. They...
, carries pheromones in rodents - Retinol binding proteinRetinol binding proteinRetinol-binding proteins are a family of proteins with diverse functions. They are carrier proteins that bind retinol.Assessment of retinol-binding protein is used to determine visceral protein mass in nutritional studies related to health.-Genes:...
, carries retinolRetinolRetinol is one of the animal forms of vitamin A. It is a diterpenoid and an alcohol. It is convertible to other forms of vitamin A, and the retinyl ester derivative of the alcohol serves as the storage form of the vitamin in animals.... - Sex hormone-binding globulin, carries sex hormones, specifically testosterone and estradiol
- Thyroxine-binding globulinThyroxine-binding globulinThyroxine-binding globulin binds thyroid hormone in circulation. It is one of three proteins responsible for carrying the thyroid hormones thyroxine and 3,5,3’-triiodothyronine in the bloodstream. Of these three proteins, TBG has the highest affinity for T4 and T3, but is present in the lowest...
, carries the thyroid hormones thyroxine (T4) and 3,5,3’-triiodothyronine (T3) - TransthyretinTransthyretinTransthyretin is a serum and cerebrospinal fluid carrier of the thyroid hormone thyroxine and retinol binding protein bound to retinol. This is how transthyretin gained its name, transports thyroxine and retinol...
, carries the thyroid hormone thyroxine (T4) - TransferrinTransferrinTransferrins are iron-binding blood plasma glycoproteins that control the level of free iron in biological fluids. In humans, it is encoded by the TF gene.Transferrin is a glycoprotein that binds iron very tightly but reversibly...
, carries iron ions in the ferricFerricFerric refers to iron-containing materials or compounds. In chemistry the term is reserved for iron with an oxidation number of +3, also denoted iron or Fe3+. On the other hand, ferrous refers to iron with oxidation number of +2, denoted iron or Fe2+...
form (Fe3+) - Vitamin D binding protein, carries vitamin DVitamin DVitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....
Hormones
- Insulin-like growth factor 1Insulin-like growth factor 1Insulin-like growth factor 1 also known as somatomedin C is a protein that in humans is encoded by the IGF1 gene. IGF-1 has also been referred to as a "sulfation factor" and its effects were termed "nonsuppressible insulin-like activity" in the 1970s.IGF-1 is a hormone similar in molecular...
, a polypeptide proteinProteinProteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
hormoneHormoneA hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
which plays an important role in childhood growth and continues to have anabolic effectsAnabolismAnabolism is the set of metabolic pathways that construct molecules from smaller units. These reactions require energy. One way of categorizing metabolic processes, whether at the cellular, organ or organism level is as 'anabolic' or as 'catabolic', which is the opposite...
in adults - ThrombopoietinThrombopoietinThrombopoietin also known as megakaryocyte growth and development factor is a protein that in humans is encoded by the THPO gene....
, a glycoproteinGlycoproteinGlycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
hormoneHormoneA hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
that regulates the production of plateletPlateletPlatelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
s by the bone marrowBone marrowBone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...
Prohormones
- Angiotensinogen, when converted to angiotensinAngiotensinAngiotensin, a peptide hormone, causes blood vessels to constrict, and drives blood pressure up. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex...
causes vasoconstriction and release of aldosterone, in effect increasing blood pressure