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peptide,

organic compound composed of amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
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 linked together chemically by peptide bonds. The peptide bond always involves a single covalent link between the α-carboxyl (oxygen-bearing carbon) of one amino acid and the amino nitrogen of a second amino acid. In the formation of a peptide bond from two amino acids, a molecule of water is eliminated. Small peptides with fewer than about ten constituent amino acids are called oligopeptides, and peptides with more than ten amino acids are termed polypeptides. Compounds with molecular weights of more than 10,000 (50–100 amino acids) are usually termed proteins. Organisms commonly contain appreciable quantities of low-molecular-weight peptides some arising from proteins while others are synthesized directly. Certain of these molecules are unusual in that they incorporate amino acids not found in proteins such as amino acids of the d-configuration. Among the biological peptides are many with physiological or antibacterial activity, such as the peptide hormones oxytocinoxytocin
, hormone released from the posterior lobe of the pituitary gland that facilitates uterine contractions and the milk-ejection reflex. The structure of oxytocin, a cyclic peptide consisting of nine amino acids, was determined in 1953 and in the same year it was
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 and vasopressin; adrenocorticotropic hormoneadrenocorticotropic hormone
, polypeptide hormone secreted by the anterior pituitary gland. Its chief function is to stimulate the cortex of the adrenal gland to secrete adrenocortical steroids, chief among them cortisone.
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 (ACTH), secreted by the pituitary gland; and several cyclic peptides, in which the amino-acid sequence forms a ring structure rather than a straight chain, such as the antibiotics tyrocidin and gramicidingramicidin
, antibiotic obtained from the bacterial species Bacillus brevis, which is found in soil. Gramicidin is particularly effective against gram-positive bacteria (see Gram's stain).
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. Laboratory synthesis of peptides has risen to the level of a well-defined art in recent years. Synthetic peptides, composed of as many as a hundred amino acids in specified sequence, have been prepared in the laboratory with good purity and high yields.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/

Peptide

A compound that is made up of two or more amino acids joined by covalent bonds which are formed by the elimination of a molecule of H2O from the amino group of one amino acid and the carboxyl group of the next amino acid. Peptides larger than about 50 amino acid residues are usually classified as proteins. Glutathione is the most abundant peptide in mammalian tissue. Hormones such as oxytocin (8), vasopressin (8), glucagon (29), and adrenocorticotropic hormone (39) are peptides whose structures have been deduced; in parentheses are the numbers of amino acid residues for each peptide.

For each step in the biological synthesis of a peptide or protein there is a specific enzyme or enzyme complex that catalyzes each reaction in an ordered fashion along the biosynthetic route. However, it is noteworthy that, although the biological synthesis of proteins is directed by messenger RNA on cellular structures called ribosomes, the biological synthesis of peptides does not require either messenger RNA or ribosomes. See Amino acids, Protein, Ribonucleic acid (RNA), Ribosomes

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Peptide

 

an organic substance consisting of identical or different amino-acid residues joined by peptide bonds. Peptides are classified according to the number of component amino-acid residues as dipeptides, tripeptides, tetrapeptides, and so on, and as polypeptides.

Small quantities of low-molecular-weight peptides occur in nearly all living cells. For example, the tripeptide glutathione is widely distributed in plant and animal tissues, and the dipeptides anserine and carnosine are present in the muscle tissue of vertebrates. Many natural biologically active substances are classified as peptides, including certain hormones (insulin, adrenocortico-trophic hormone, glucagon, vasopressin, oxytocin), antibiotics (gramicidin, bacillin), and angiotensins and kinins, which are present in blood plasma.

The peptide molecule is a linear or branched chain. If the molecule is linear, it has two termini with one terminal amino group (—NH2) and one terminal carboxyl group (—COOH). Peptides with a closed-chain structure are called cyclopeptides, which include many bacterial toxins, hormones, and antibiotics. Many natural peptides contain amino acids that are not present in proteins, for example, D-amino acids. Peptides exhibit amphoteric properties, give biuret (beginning with tripeptides) and ninhydrin reactions, and dissolve readily in water, acids, and alkalies but are practically insoluble in organic solvents. They decompose upon heating to 200°-300°C.

In living cells, peptides are synthesized from amino acids or formed during the enzymatic breakdown of proteins. Chemical synthesis is used to obtain many biologically active natural peptides and their numerous analogues. Advancements in peptide chemistry have resolved many complex problems in modern biochemistry and molecular biology, such as the deciphering of the genetic code.

REFERENCE

Khimiia biologicheski aktivnykh prirodnykh soedinenii. Moscow, 1970.

N. N. CHERNOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

peptide

[′pep‚tīd]
(biochemistry)
A compound of two or more amino acids joined by peptide bonds.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

peptide

any of a group of compounds consisting of two or more amino acids linked by chemical bonding between their respective carboxyl and amino groups
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
[5] Human genes: NPPC, C-type natriuretic peptide; NPPA, atrial natriuretic peptide; NPPB, B-type natriuretic peptide; NPR2, natriuretic peptide receptor B.
Mebazaa, "Lowered B-type natriuretic peptide in response to levosimendan or dobutamine treatment is associated with improved survival in patients with severe acutely decompensated heart failure," Journal of the American College ofCardiology, vol.
Usefulness of serial monitoring of B-type natriuretic peptide for the detection of acute rejection after heart transplantation.
The prognostic value of B-type natriuretic peptide in patients with acute coronary syndromes.
There are scant data available at present to indicate that testing for B-type natriuretic peptides improves inpatient medical outcomes, and there are only limited data concerning the potential impact of natriuretic peptide testing on hospital LOS and financial outcomes.
The plasma B-type natriuretic peptide (BNP) test is a rapid, relatively inexpensive point-of-care test approved for diagnosis of heart failure in patients presenting with shortness of breath to the emergency department and other acute care settings.
Assay of the B-type natriuretic peptide also contributes to standard clinical information in the diagnosis of congestive heart failure.
B-type natriuretic peptide level fell from a mean of 329 pg/mL to 281 pg/mL in the tai chi group, and rose from a mean of 285 pg/mL to 306 pg/mL in the control group.
B-type natriuretic peptide is secreted by the left ventricle when the heart is unable to pump blood efficiently.
In emergency patients complaining of shortness of breath, Maisel and his colleagues administered the simple blood test to measure the presence of a hormone called B-type natriuretic peptide (BNP) that is secreted from the heart's ventricles in response to increased pressure and volume in the organ.
Natrecor is the first of a new drug class and is a recombinant form of B-type natriuretic peptide (BNP), a hormone secreted by the heart in response to heart failure.
B-type natriuretic peptide is released from the cardiac ventricles and plasma concentrations reflect ventricular systolic function.