peptide

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.