peptide

Physiology

(noun)

A class of organic compounds consisting of various numbers of amino acids in which the amine of one is reacted with the carboxylic acid of the next to form anamide bond.

Related Terms

  • amphipathic
  • antimicrobial resistance
Microbiology

(noun)

A class of organic compounds consisting of various numbers of amino acids, in which the amine of one is reacted with the carboxylic acid of the next to form an amide bond.

Related Terms

  • siderophores
  • metabolite

Examples of peptide in the following topics:

  • Nonribosomal Peptide Antibiotics

    • Nonribosomal peptides (NRP) are a class of peptide secondary metabolites which can function as antibiotics.
    • Nonribosomal peptides (NRP) are a class of peptide secondary metabolites, usually produced by microorganisms like bacteria and fungi.
    • Nonribosomal peptides are synthesized by nonribosomal peptide synthetases, which, unlike the ribosomes, are independent of messenger RNA.
    • Each nonribosomal peptide synthetase can synthesize only one type of peptide.
    • Nonribosomal peptides are synthesized by one or more specialized nonribosomal peptide-synthetase (NRPS) enzymes.
  • Peptides & Proteins

    • As expected, the free amine and carboxylic acid functions on a peptide chain form a zwitterionic structure at their isoelectric pH.
    • The conformational flexibility of peptide chains is limited chiefly to rotations about the bonds leading to the alpha-carbon atoms.
    • This restriction is due to the rigid nature of the amide (peptide) bond.
    • This keeps the peptide links relatively planar and resistant to conformational change.
    • This aspect of peptide structure is an important factor influencing the conformations adopted by proteins and large peptides.
  • Antimicrobial Peptides

    • In contrast to the clonal, acquired adaptive immunity, endogenous peptide antibiotics or antimicrobial peptides provide a fast and energy-effective mechanism as front-line defense.
    • Antimicrobial peptides (AMPs) are small molecular weight proteins with broad spectrum antimicrobial activity against bacteria, viruses, and fungi.
    • Peptides of the defensin, cathelicidin, and histatin classes are found in humans .
    • Once in a target microbial membrane, the peptide kills target cells through diverse mechanisms.
    • Decreased levels of these peptides have been noted for patients with atopic dermatitis and Kostmann's syndrome, a congenital neutropenia.
  • Antimicrobial Peptides

    • Antimicrobial peptides (also called host defense peptides) are an evolutionarily conserved component of the innate immune response and are found among all classes of life.
    • Antimicrobial peptides generally consist of between 12 and 50 amino acids.
    • The initial contact between the peptide and the target organism is electrostatic, as most bacterial surfaces are anionic, or hydrophobic, such as in the antimicrobial peptide Piscidin.
    • It appears as though many peptides initially isolated and termed as "antimicrobial peptides" have been shown to have more significant alternative functions in vivo (e.g. hepcidin).
    • Several methods have been used to determine the mechanisms of antimicrobial peptide activity.
  • Peptide Bonding between Amino Acids

    • The peptide bond is an amide bond which links amino acids together to form proteins.
    • A peptides is a molecule composed of two or more amino acids.
    • The extra stabilization makes the peptide bond relatively stable and unreactive.
    • The peptide bond (circled) links two amino acids together.
    • Identify the amino acids that were combined to create a peptide.
  • Antimicrobial Proteins

    • Antimicrobial peptides (also called host defense peptides) are an evolutionarily-conserved component of the innate immune response found among all known species.
    • Antimicrobial peptides are a unique and diverse group of molecules.
    • As peptides, they consist of chains of amino acids that determine their composition and structure.
    • This causes the peptide to bind to bacterial membranes instead of host cell membranes.
    • Describe the role of antimicrobial peptides in the innate immune system
  • Chemistry of Hormones

    • There are three classes of hormones: peptide hormones, lipid hormones, and monoamine hormones.
    • Peptide hormones consist of short chains of amino acids, such as vasopressin, that are secreted by the pituitary gland and regulate osmotic balance; or long chains, such as insulin, that are secreted by the pancreas, which regulates glucose metabolism.
    • Some peptide hormones contain carbohydrate side chains  and are termed glyco-proteins, such as the follicle-stimulating hormone.
    • All peptide hormones are hydrophilic and are therefore unable to cross the plasma membrane alone.
  • Lipid-Derived, Amino Acid-Derived, and Peptide Hormones

    • All hormones in the human body can be divided into lipid-derived, amino acid-derived, and peptide hormones.
    • Although there are many different hormones in the human body, they can be divided into three classes based on their chemical structure: lipid-derived, amino acid-derived, and peptide hormones (which includes peptides and proteins).
    • As a result, they remain in circulation longer than peptide hormones.
    • The structure of peptide hormones is that of a polypeptide chain (chain of amino acids).
    • These peptide hormones are much larger than those derived from cholesterol or amino acids.
  • The Primary Structure of Peptides

    • Because the N-terminus of a peptide chain is distinct from the C-terminus, a small peptide composed of different aminoacids may have a several constitutional isomers.
    • Natural peptides of varying complexity are abundant.
    • The different amino acids that make up a peptide or protein, and the order in which they are joined together by peptide bonds is referred to as the primary structure.
    • If the carboxyl function at the C-terminus of a peptide forms a peptide bond with the N-terminal amine group a cyclic peptide is formed.
    • Arrows on these bonds point in the CO-N direction of each peptide bond.
  • Protease Inhibitors

    • Proteases are enzymes that have the ability to cut proteins into peptides.
    • Protease inhibitors are short peptide-like molecules that are competitive inhibitors of the enzyme.
    • Instead of -NH-CO- peptide link, they contain -(CH2-CH(OH)-).
    • Saquinavir is the first clinically used peptide-like inhibitor.
    • Some protease inhibitors do not mimic peptides in their structure.
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