Biochemical characterization of MelJ and MelK

Novel Methoxymethacrylate Natural Products Uncovered by Statistics-Based Mining of the Myxococcus fulvus Secondary Metabolome

This study reports the uncovering of new myxobacterial natural products through comprehensive analysis of the Myxococcus fulvus secondary metabolome. Statistics-based mining of mass spectrometry data paved the way for full structure elucidation of two new secondary metabolites named fulvuthiacene A and B, and investigation of the underlying biosynthetic pathway revealed an evolutionary link between the fulvuthiacene hybrid polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) gene cluster and the related myxothiazol and melithiazol assembly lines. Detailed characterization of the post-PKS modification enzyme cascade responsible for the fulvuthiacenes' terminal β-methoxy-methyl acrylate moiety was pursued by heterologous expression of these enzymes in the myxothiazol producer Stigmatella aurantiaca DW4/3-1. The discovery of fulvuthiacenes provides new insights into the overall structure-activity relationship picture for the β-methoxyacrylate class of respiratory chain inhibitors and might thus serve as starting point for the development of next-generation β-methoxymethacrylate fungicides.

Interrupted adenylation domains: unique bifunctional enzymes involved in nonribosomal peptide biosynthesis

Nonribosomal peptides (NRPs) account for a large portion of drugs and drug leads currently available in the pharmaceutical industry. They are one of two main families of natural products biosynthesized on megaenzyme assembly-lines composed of multiple modules that are, in general, each comprised of three core domains and on occasion of accompanying auxiliary domains. The core adenylation (A) domains are known to delineate the identity of the specific chemical components to be incorporated into the growing NRPs. Previously believed to be inactive, A domains interrupted by auxiliary enzymes have recently been proven to be active and capable of performing two distinct chemical reactions. This highlight summarizes current knowledge on A domains and presents the various interrupted A domains found in a number of nonribosomal peptide synthetase (NRPS) assembly-lines, their predicted or proven dual functions, and their potential for manipulation and engineering for chemoenzymatic synthesis of new pharmaceutical agents with increased potency.

Function of the loading module in CorI and of the O-methyltransferase CorH in vinyl carbamate biosynthesis of the antibiotic corallopyronin A

Corallopyronin A is a promising in vivo active antibiotic, currently undergoing preclinical evaluation. This myxobacterial compound interferes with a newly identified drug target site, i.e., the switch region of the bacterial DNA-dependent RNA-polymerase (RNAP). Since this target site differs from that of known RNAP inhibitors such as the rifamycins, corallopyronin A shows no cross-resistance with other antibacterial agents. Corallopyronin A is a polyketide synthase- and nonribosomal peptide synthetase-derived molecule whose structure and biosynthesis is distinguished by several peculiarities, such as the unusual vinyl carbamate functionality whose formation involves carbonic acid as an unprecedented C1-starter unit. Using in vitro experiments the nature of this starter molecule was revealed to be the methyl ester of carbonic acid. Biochemical investigations showed that methylation of carbonic acid is performed by the O-methyltransferase CorH. These experiments shed light on the biosynthesis of the Eastern chain of α-pyrone antibiotics such as corallopyronin A.