Polyketide
Overview
 
Polyketides are secondary metabolites from bacteria, fungi, plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s, and animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s. Polyketides are usually biosynthesized
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

 through the decarboxylative condensation
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...

 of malonyl-CoA
Malonyl-CoA
Malonyl-CoA is a coenzyme A derivative.-Functions:It plays a key role in chain elongation in fatty acid biosynthesis and polyketide biosynthesis....

 derived extender units in a similar process to fatty acid synthesis (a Claisen condensation
Claisen condensation
The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone...

). The polyketide chains produced by a minimal polyketide synthase
Polyketide synthase
Polyketide synthases are a family of multi-domain enzymes or enzyme complexes that produce polyketides, a large class of secondary metabolites, in bacteria, fungi, plants, and a few animal lineages...

 are often further derivitized
Derivative (chemistry)
In chemistry, a derivative is a compound that is derived from a similar compound by some chemical or physical process. In the past it was also used to mean a compound that can be imagined to arise from another compound, if one atom is replaced with another atom or group of atoms, but modern...

 and modified into bioactive natural product
Natural product
A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...

s.

Polyketides are structurally a very diverse family of natural products with diverse biological activities and pharmacological properties.
Encyclopedia
Polyketides are secondary metabolites from bacteria, fungi, plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s, and animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s. Polyketides are usually biosynthesized
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

 through the decarboxylative condensation
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...

 of malonyl-CoA
Malonyl-CoA
Malonyl-CoA is a coenzyme A derivative.-Functions:It plays a key role in chain elongation in fatty acid biosynthesis and polyketide biosynthesis....

 derived extender units in a similar process to fatty acid synthesis (a Claisen condensation
Claisen condensation
The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone...

). The polyketide chains produced by a minimal polyketide synthase
Polyketide synthase
Polyketide synthases are a family of multi-domain enzymes or enzyme complexes that produce polyketides, a large class of secondary metabolites, in bacteria, fungi, plants, and a few animal lineages...

 are often further derivitized
Derivative (chemistry)
In chemistry, a derivative is a compound that is derived from a similar compound by some chemical or physical process. In the past it was also used to mean a compound that can be imagined to arise from another compound, if one atom is replaced with another atom or group of atoms, but modern...

 and modified into bioactive natural product
Natural product
A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...

s.

Polyketides are structurally a very diverse family of natural products with diverse biological activities and pharmacological properties. They are broadly divided into three classes: type I polyketides (often macrolides produced by multimodular megasynthases), type II polyketides (often aromatic molecules produced by the iterative action of dissociated enzymes), and type III polyketides (often small aromatic molecules produced by fungal species). Polyketide antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

s, antifungals, cytostatics, anticholesteremic, antiparasitics, coccidiostat
Coccidiostat
A coccidiostat is an antiprotozoal agent that acts upon Coccidia parasites.Examples include:* amprolium* arprinocid* artemether* clopidol* decoquinate* diclazuril* dinitolmide* ethopabate* halofuginone* lasalocid* monensin* narasin* nicarbazin...

s, animal growth promoters
Growth factor
A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes....

 and natural insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

s are in commercial use.

Examples

  • Macrolide
    Macrolide
    The macrolides are a group of drugs whose activity stems from the presence of a macrolide ring, a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered...

    s
    • Pikromycin
      Pikromycin
      Pikromycin was studied by Brokmann and Hekel in 1951 and is the first antibiotic macrolide to be isolated.Pikromycin is synthesized through a type I polyketide synthase system in Streptomyces venezuelae, a species of Gram-positive bacterium in the Streptomyces genus...

      , the first isolated macrolide (1951)
    • The antibiotic
      Antibiotic
      An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

      s erythromycin A
      Erythromycin
      Erythromycin is a macrolide antibiotic that has an antimicrobial spectrum similar to or slightly wider than that of penicillin, and is often used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma and...

      , clarithromycin
      Clarithromycin
      Clarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia , skin and skin structure infections...

      , and azithromycin
      Azithromycin
      Azithromycin is an azalide, a subclass of macrolide antibiotics. Azithromycin is one of the world's best-selling antibiotics...

    • The immunosuppressant
      Immunosuppressant
      An immunosuppressant is any substance that performs immunosuppression of the immune system. They may be either exogenous, as immunosuppressive drugs, or endogenous, as ,e. g., testosterone...

       tacrolimus (FK506)
      Tacrolimus
      Tacrolimus is an immunosuppressive drug that is mainly used after allogeneic organ transplant to reduce the activity of the patient's immune system and so lower the risk of organ rejection...

    • Radicicol
      Radicicol
      Radicicol, also known as monorden, is a natural product that binds to Hsp90 and alters its function. HSP90 client proteins play important roles in the regulation of the cell cycle, cell growth, cell survival, apoptosis, angiogenesis and oncogenesis.-Further reading: Review of the chemistry and...

       and Pochonin family (HSP90
      Hsp90
      Hsp90 is a molecular chaperone and is one of the most abundant proteins expressed in cells. It is a member of the heat shock protein family, which is upregulated in response to stress...

       inhibitor)
  • Polyene
    Polyene
    Polyenes are poly-unsaturated organic compounds that contain one or more sequences of alternating double and single carbon-carbon bonds. These double carbon-carbon bonds interact in a process known as conjugation, which results in an overall lower energy state of the molecule.Organic compounds with...

     antibiotic
    Antibiotic
    An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

    s
    • Amphotericin
  • Tetracyclines
    • The tetracycline family of antibiotic
      Antibiotic
      An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

      s
  • Acetogenins
    • Annonacin
      Annonacin
      Annonacin is a chemical found in some fruits such as the guanabana . It is a member of the class of compounds known as acetogenins...

    • Uvaricin
      Uvaricin
      Uvaricin is a bis fatty acid lactone that was first isolated in 1982 from the roots of Uvaria accuminata. Uvaricin was the first in a class of compounds with potent anticancer activity known as acetogenins. Acetogenins, which are found in plants of the family Annonaceae, seem to kill cells by...

  • Others
    • Discodermolide
      Discodermolide
      -Discodermolide is a recently discovered polyketide natural product found to be a potent inhibitor of tumor cell growth. The molecule's carbon skeleton is made up of eight polypropionate and four acetate units with 13 stereocenters.-History:...

    • Aflatoxin
      Aflatoxin
      Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, the most notable ones being Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and among the most carcinogenic substances known...

    • Usnic acid
      Usnic acid
      Usnic acid is a naturally occurring dibenzofuran derivative found in several lichen species. It was first isolated by German scientist W. Knop in 1844 and first synthesized between 1933-1937 by Curd and Robertson. Usnic acid was identified in many genera of lichens including Usnea, Cladonia,...


Biosynthesis

Polyketides are synthesized by one or more specialized and highly complex polyketide synthase
Polyketide synthase
Polyketide synthases are a family of multi-domain enzymes or enzyme complexes that produce polyketides, a large class of secondary metabolites, in bacteria, fungi, plants, and a few animal lineages...

 (PKS) enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s.
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