Call us toll-free

Engineered biosynthesis of novel polyketides.

Expression of a functional fungal polyketide synthase in the bacterium Streptomyces coelicolor A3(2).

Approximate price

Pages:

275 Words

$19,50

Biosynthesis of polyketides in heterologous hosts.

The best solutions will not only be widely publicized, but are also likely to gain rapid acceptance as benchmarks for next-generation challenges. We welcome suggestions regarding how such an approach might be further tailored to catalyze rapid advances in combinatorial biosynthesis.

Engineered polyketide biosynthesis and ..

Notwithstanding encouraging progress over the past two decades [, -], the promise of rationally guided combinatorial biosynthesis remains unrealized. In the sections that follow, we discuss key ecological, enzymological, and technological challenges that must be addressed in order to efficiently synthesize libraries of “unnatural” natural products.

and meta- biosynthesis of polyketides and ..

Characterization of the Streptomyces peucetius ATCC29050 genes encoding doxorubicin polyketide synthase.

AB - The study of bioactive natural products has undergone rapid advancement with the cloning and sequencing of large number of gene clusters and the concurrent progress to manipulate complex biosynthetic systems in heterologous hosts. The genetic reconstitution necessitates that the heterologous hosts possess substrate pools that could be coordinately supplied for biosynthesis. Polyketide synthases (PKS) utilize acyl-coenzyme A (CoA) precursors and synthesize polyketides by repetitive decarboxylative condensations. Here we show that acyl-CoA ligases, which belong to a large family of acyl-activating enzymes, possess potential to produce varied starter CoA precursors that could be utilized in polyketide biosynthesis. Incidentally, such protein domains have been recognized in several PKS and nonribosomal peptide synthetase gene clusters. Our studies with mycobacterial fatty acyl-CoA ligases (FACLs) show remarkable tolerance to activate a variety of fatty acids that contain modifications at α, β, ω, and ω-ν positions. This substrate flexibility extends further such that these proteins also efficiently utilize N-acetyl cysteamine, the shorter acceptor terminal portion of CoASH, to produce acyl-SNACs. We show that the in situ generated acyl-CoAs and acyl-SNACs could be channeled to types I and -III PKS systems to produce new metabolites. Together, the promiscuous activity of FACL and PKSs provides new opportunities to expand the repertoire of natural products.

N2 - The study of bioactive natural products has undergone rapid advancement with the cloning and sequencing of large number of gene clusters and the concurrent progress to manipulate complex biosynthetic systems in heterologous hosts. The genetic reconstitution necessitates that the heterologous hosts possess substrate pools that could be coordinately supplied for biosynthesis. Polyketide synthases (PKS) utilize acyl-coenzyme A (CoA) precursors and synthesize polyketides by repetitive decarboxylative condensations. Here we show that acyl-CoA ligases, which belong to a large family of acyl-activating enzymes, possess potential to produce varied starter CoA precursors that could be utilized in polyketide biosynthesis. Incidentally, such protein domains have been recognized in several PKS and nonribosomal peptide synthetase gene clusters. Our studies with mycobacterial fatty acyl-CoA ligases (FACLs) show remarkable tolerance to activate a variety of fatty acids that contain modifications at α, β, ω, and ω-ν positions. This substrate flexibility extends further such that these proteins also efficiently utilize N-acetyl cysteamine, the shorter acceptor terminal portion of CoASH, to produce acyl-SNACs. We show that the in situ generated acyl-CoAs and acyl-SNACs could be channeled to types I and -III PKS systems to produce new metabolites. Together, the promiscuous activity of FACL and PKSs provides new opportunities to expand the repertoire of natural products.

Biosynthesis of bacterial aromatic polyketides

24/11/2009 · Heterologous production of polyketides in hosts such as Streptomyces ..

In this review, combinatorial biosynthesis is defined as the genetic manipulation of two or more enzymes involved in polyketide biosynthesis. According to this enzyme-centric definition, combinatorial biosynthesis could even yield the natural product itself, as long as the corresponding polyketide synthase (PKS) harbors two or more genetically modified enzymes. These enzymatic modifications can be accomplished by either genetic manipulation of the original enzyme or by replacing it with a homolog (although the latter approach is more common at the present time). By contrast, a product-centric definition of combinatorial biosynthesis would encompass natural product analogs with two or more functional group transformations, regardless of how these modifications are achieved. For example, products of combinatorial biosynthesis could be derived via precursor directed biosynthesis or through other metabolic engineering strategies []. We have chosen an enzyme-centric definition because, in our opinion, it highlights the fundamental and technological challenges to exploiting the functional modularity of PKSs []. Specifically, combinatorial biosynthesis can be achieved by manipulating enzymes responsible for primer unit incorporation, chain elongation, and chain termination.

Until recently, a major obstacle to combinatorial biosynthesis was the availability of DNA sequences of an adequately large number of cloned PKS genes. Less than 20 multifunctional PKS gene clusters had been fully sequenced by the turn of the millennium. As high-throughput sequencing techniques gained momentum, this number increased exponentially. Whereas the growth in PKSs corresponding to structurally characterized natural products has remained modest, the emergence of whole genome sequencing methods has resulted in the discovery of cryptic gene clusters at an explosive pace (). Not only has there been an immense growth in the repertoire of enzyme domains and modules, but new assembly line architectures have also been discovered (e.g., “AT-less” PKSs [, ]). Today, an aspiring biosynthetic engineer has access to a virtually infinite palette of genetic raw material, although much of it remains to be functionally decoded.

Biosynthesis of polyketides in heterologous hosts
Order now
  • Biosynthesis of polyketides in heterologous hosts.

    biosynthesis of polyketides ..

  • Biosynthesis of Polyketides in Heterologous Hosts

    Engineered biosynthesis of novel polyketides.

  • Combinatorial Biosynthesis of Polyketides ..

    the engineered biosynthesis of polyketides ..

Order now

complex biosynthetic pathways in heterologous hosts

In addition to the above challenges in basic biology and chemistry, the toolbox for combinatorial manipulation of PKSs must also be improved. The rapid growth in PKS sequences () will likely accelerate further, as methods for automated assembly of genome-sized contigs from GC-rich organisms are improved. Together with the rapidly decreasing cost of oligonucleotides, this could enable assembly of expression constructs for full-length (i.e. 30-100 kb) natural or modified PKS genes []. Of course, heterologous hosts capable of functionally expressing these PKS pathways must be available. Whereas no single host is capable of expressing all types of PKS pathways, Escherichia coli and hosts such as Streptomyces coelicolor and its close relative Streptomyces lividans appear to have a broad scope for this purpose. The key remaining challenge is to improve the polyketide productivity of these hosts. Our own experience suggests that productivity in heterologous hosts is most often not limited by the PKS itself, because specific polyketide productivity is higher in native hosts, even though PKS protein levels are higher in the heterologous host. This is an important challenge for the metabolic engineer [].

Combinatorial Biosynthesis of Polyketides – A Perspective

At its core, combinatorial biosynthesis of assembly line PKSs is an exercise in enzyme engineering that rests upon two crucial assumptions. First, individual enzymes along the assembly line must have relaxed substrate specificity. Second, the mechanisms that promote channeling of biosynthetic intermediates from one enzyme to the next must be sufficiently conserved in order to permit the engineering of chimeric assembly lines. Available evidence suggests that both hypotheses are plausible, but lack thorough validation. In the remainder of this section, we review the experimental evidence supporting these hypotheses.

[22 x Biosynthesis of complex polyketides in a ..

Along with improved methods for PKS cloning and expression, superior methods for detecting and characterizing polyketide products are also needed. Advances in microscale NMR spectroscopy already allow structure elucidation of new natural products with as little as a few nanomoles, thus reducing the sample size by 2-3 orders of magnitude []. Similarly, new techniques for ionization and detection of natural products via mass spectrometry open the door to the characterization of very small samples []. In both approaches, the problem of contaminants can be particularly vexing. Therefore, robust workflows need to be developed for analyzing trace quantities of a new compound made by an engineered bacterium. Here too, the use of heterologous hosts is an advantage, as isotope-tagging methods could be implemented to differentiate polyketide products from background contaminants.

Order now
  • Kim

    "I have always been impressed by the quick turnaround and your thoroughness. Easily the most professional essay writing service on the web."

  • Paul

    "Your assistance and the first class service is much appreciated. My essay reads so well and without your help I'm sure I would have been marked down again on grammar and syntax."

  • Ellen

    "Thanks again for your excellent work with my assignments. No doubts you're true experts at what you do and very approachable."

  • Joyce

    "Very professional, cheap and friendly service. Thanks for writing two important essays for me, I wouldn't have written it myself because of the tight deadline."

  • Albert

    "Thanks for your cautious eye, attention to detail and overall superb service. Thanks to you, now I am confident that I can submit my term paper on time."

  • Mary

    "Thank you for the GREAT work you have done. Just wanted to tell that I'm very happy with my essay and will get back with more assignments soon."

Ready to tackle your homework?

Place an order