"Biosynthesis of polyketides." .
Additionally,it has been reported that the use of 13C labeled acetate isbecoming increasingly common in the study of polyketide biosynthesis ().
Structures and Mechanisms of Polyketide Synthases - …
AB - Fumonisins are polyketide-derived mycotoxins produced by several plant pathogenic fungi. The toxins cause several fatal diseases in domestic animals and are associated with esophageal cancer and neural tube defects in humans. Fumonisins contain a highly reduced, acyclic 18-carbon chain, which is synthesized by an iterative polyketide synthase (PKS). This PKS does not contain a thioesterase or cyclase domain that is found in other PKSs for the release of the covalently linked polyketide chain. In this study, we expressed the acyl carrier protein (ACP) of FUM1 and in vitro loaded acyl chains to the ACP from acyl-CoA using a promiscuous 4′-phosphopantetheinyl transferase. We then expressed FUM8, which is homologous to 2-oxoamine synthase genes, in yeast and showed that the enzyme is able to offload the acyl chains from ACP. Products resulted from the decarboxylative condensation between L-alanine and acyl-S-ACP were detected by GC-MS. The enzyme activity was dependent on pyridoxal 5′-phosphate (PLP), and C18-S-ACP was the preferred substrate. The results revealed a novel polyketide chain-releasing mechanism, in which a PLP-dependent enzyme catalyzes the termination and offloading of the polyketide chain as well as the introduction of a new carbon-carbon bond and an amino group to the chain. The mechanism is fundamentally different from the thioesterase/cyclase- catalyzed polyketide chain release found in bacterial and other fungal polyketide biosyntheses.
We combine expertise in moleculargenetics, fungal biology and microbiology, polyketide biosynthesis in bacteriaand fungi (particularly of iterative systems), gene expression and proteinpurification, chemical synthesis and analysis, natural products chemistry andanalytical chemistry.
Polyketide | Alkene | Biosynthesis
Recently, there has been much progress made toward the goal of characterizingthe enzymes that catalyze the chain elongation and cyclization reactionsleading towards aromatic polyketides.
Polyketides Biosynthesis - an overview | ScienceDirect …
N2 - Polyketides (PKs) are a large group of natural products produced by microorganisms and plants. They are biopolymers of acetate and other short carboxylates and are biosynthesized by multifunctional enzymes called polyketide synthases (PKSs). This review discusses the biosynthesis of four toxic PK, aflatoxins, fumonisins, ochratoxins (OTs), and zearalenone. These metabolites are structurally diverse and differ in their mechanisms of toxicity. However, they are all of concern in food safety and agriculture because of their toxic properties and their frequent accumulation in crops used for food and feed. The focus is on the recent advancements in the understanding of the molecular mechanisms for the biosynthesis of these mycotoxins. Several of the mycotoxin PKSs have been genetically and biochemically studied while other PKSs remain to be investigated. Multiple post-PKS modifications are often required for the maturation of the mycotoxins. Many of these modification steps for aflatoxins and fumonisins are well established while the post-PKS modifications for zearalenone and OTs remain to be biochemically characterized. More efforts are needed to completely illustrate the biosynthetic mechanisms for this important group of PKs.
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Therefore, much ofthe dogma that describes polyketide synthesis and characterizes the enzymespurportedly involved has been extrapolated from the well characterizedpolypeptides and mechanisms of long chain fatty acid synthesis ().
Polyketide biosynthesis has been well studied and there are ..
The implicit,but unstated (by ) assumption that chemicalmechanisms should be recognizable in biosynthetic processes, even thoughenzymes and coenzymes are clearly important, is a reoccurring theme inthe hypothetical mechanism of polyketide biosynthesis.