Tetrahydroxynaphthalene synthase

Ku et al. [434] demonstrated that microreactors can also be used for tandem reactions. A microreactor containing beads functionalized with polyketide synthase [1,3,6,8-tetrahydroxynaphthalene synthase (THNS)] was coupled to one that contained soybean peroxidase (SBP). THNS was immobilized using the Ni-NTA method... 

The strucmral and kinetic data on chalcone synthase and related PKS Ills have been used to develop a model that explains how these enzymes control loading, condensation, and cyclization reactions in one active site. The attention of readers is drawn to an excellent review by Austin and Noel in which the structure and mechanism of plant and bacterial PKS III homologs have been compared and contrasted. Several noteworthy points from their analyses include a discussion on the bacterial PKS III enzymes that contain multiple cysteine residues in their active sites, such as tetrahydroxynaphthalene synthase and DpgA, a PKS III involved in dihydroxyphenylglycine synthesis, and the possibility that some bacterial PKS III enzymes may use AGP as the substrate carrier. 

Enzymatic syntheses within the microfluidic platform were also reported. The construction and novel compound synthesis from a synthetic metabolic pathway consisting of a type III poly-ketide synthase (PKS) known as 1,3,6,8-tetrahydroxynaphthalene synthase (THNS) from Streptomyces coelicolor and soybean peroxidase (SBP) in a microreactor were performed (Fig. 5) [11]. THNS immobilized to Ni-NTA agarose... 

Enzymatic syntheses within the microfluidic platform were also reported. The construction and novel compound synthesis from a synthetic metabolic pathway consisting of a type HI polyketide synthase (PKS) known as 1,3,6,8-tetrahydroxynaphthalene synthase (THNS) from Streptomyces coelicolor and soybean peroxidase (SBP) in a microreactor were performed (Fig. 5) [11]. THNS immobilized to Ni-NTA agarose beads was prepacked into a microfluidic channel, while SBP was covalently attached to the walls of a second microfluidic channel precoated with a reactive poly(maleic anhydride) derivative. The result was a tandem, two-step hiochip that enabled synthesis of novel polyketide derivatives. The first microchan-nel, consisting of THNS, resulted in the conversion of malonyl-CoA to flaviolin in yields of up to 40% with a residence time of 6 min. This conversion is similar to that obtained in several-milliliter batch reactions after 2 h. Linking this microchannel to the SBP microchannel results in biflaviolin synthesis. During the course of this work, we discovered that the substrate specificity of THNS could be manipulated by simply changing the reaction pH. As a result, the starter acyl-CoA specificity can be broadened to yield a series of truncated pyrone products. When combined with variations in the ratio of acyl-CoA and... 

CHS-related enzymes are also found in microorganisms and appear to be responsible for the formation of the pentaketide 1,3,6,8-tetrahydroxynaphthalene (10) in Streptomyces griseusP While flavonoids are widely distributed in plants, chlorflavonin (72) has been isolated from the frmgus Aspergillus candicusP although nothing is currently known of the nature of the associated synthase. 

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