polyketide biosynthetic process

A large number of such reactions are used in synthetic organic chemistry. Other examples include:
Photo provided by Flickr

negative regulation of polyketide biosynthetic process (4)

Teartasin, W, Limpkin, C, Glod, F, Spencer, J, Cox, RJ, Simpson, TJ, Crosby, J, Crump, MP and Hadfield, AT (2004) Expression, purification and preliminary X-ray diffraction analysis of a ketoreductase from a type II polyketide synthase. 60:1137-8

positive regulation of polyketide biosynthetic process (4)
Photo provided by Flickr

regulation of polyketide biosynthetic process (6)

In one type of polymerization reaction, a series of condensation steps take place whereby or monomer chains add to each other to form longer chains. This is termed 'condensation polymerization' or '', and occurs for example in the synthesis of or . It may be either a homopolymerization of a single monomer A-B with two different end groups which condense, or a of two co-monomers A-A and B-B. Small molecules are usually liberated in these condensation steps, in contrast to reactions with no liberation of small molecules.

polyketide biosynthetic process"The following 8 pages are in this category, out of 8 total.
Photo provided by Flickr

Polyketides are structurally a very diverse family of naturalproducts with diverse biological activities and pharmacologicalproperties. They are broadly divided into three classes: type Ipolyketides (often macrolides produced by mutimodularmegasynthaes), type II polyketides (often aromatic moleculesproduced by the iterative action of dissociated enzymes), and typeIII polyketides (often small aromatic molecules produced by fungalspecies). Polyketide , , , anticholesterolemics,antiparasitics, coccidiostatics, animal growth promoters andnatural are in commercial use.

regulation of polyketide biosynthetic process
Photo provided by Flickr


Category:GO:0030639 ! polyketide biosynthetic process …

The loading acyltransferase (AT) domains of modular polyketide synthases (PKSs) control the choice of starter units incorporated into polyketides and are therefore attractive targets for the engineering of modular PKSs. Here, we report the structural and biochemical characterizations of the loading AT from avermectin modular PKS, which accepts more than 40 carboxylic acids as alternative starter units for the biosynthesis of a series of congeners. This first structural analysis of loading ATs from modular PKSs revealed the molecular basis for the relaxed substrate specificity. Residues important for substrate binding and discrimination were predicted by modeling a substrate into the active site. A mutant with altered specificity toward a panel of synthetic substrate mimics was generated by site-directed mutagenesis of the active site residues. The hydrolysis of the N-acetylcysteamine thioesters of racemic 2-methylbutyric acid confirmed the stereospecificity of the avermectin loading AT for an configuration at the C-2 position of the substrate. Together, these results set the stage for region-specific modification of polyketides through active site engineering of loading AT domains of modular PKSs.

polyketide biosynthetic process

This process is very similar to , by and to Type I . But, incontrast to synthesis, the ofthe growing polyketide chain are not modified during chainelongation and they are not usually fully . In contrast to Type I PKS systems, thesynthetic enzymes (KS, CLF, ACP and AT) are not attached to eachother, and may not even remain associated during each step of thepolyketide chain synthesis.

"polyketide synthesis" EXACT [] ..

Polyketides are from , , , and . Polyketides are usually through the decarboxylative condensation of derived extender units in asimilar process to (a ). The polyketide chains produced by a minimal polyketide synthase areoften further derivitized and modified into bioactive .

Polyketide synthases use a similar ..

After the 21-carbon decaketide chain of DXR is completed,successive modifications are made to eventually produce a aglycone(without attached) .The , activatedby addition of TDP, is created in another series of reactions .It is joined to the aglycone and furthermodifications are done to produce first then DXR .There are at least 3 important to DXR : dps which specify the required for the linearpolyketide chain synthesis and its first cyclizations, the dnrcluster is responsible for the remaining modifications of the structure and the dnm genes involved in the , , synthesis. Additionally, thereis a set of "self resistance" to reduce the toxic impact of the onthe producing .One mechanism is a pump that causes of the DXR out of the cell(drr ).Since these complex molecules are only advantageous under specificconditions, and require a lot of energy to produce, their synthesisis tightly regulated.