Emergent Repair of a Perforated Giant Duodenal Ulcer in a Patient With an Unmanaged Ulcer History.

Giant duodenal ulcers (GDUs) are full-thickness disruptions of the gastrointestinal epithelium greater than 3cm in diameter. The significant size and disease chronicity lead to deleterious outcomes and high mortality risk if ulcer progression is not halted. While still prevalent in developing countries, GDUs are increasingly rare in industrialized nations.

Biocatalytic synthesis of pikromycin, methymycin, neomethymycin, novamethymycin, and ketomethymycin.

A biocatalytic platform that employs the final two monomodular type I polyketide synthases of the pikromycin pathway in vitro followed by direct appendage of D-desosamine and final C-H oxidation(s) in vivo was developed and applied toward the synthesis of a suite of 12- and 14-membered ring macrolide natural products. This methodology delivered both compound classes in 13 steps (longest linear sequence) from commercially available (R)-Roche ester in >10% overall yields.

Structural basis of functional group activation by sulfotransferases in complex metabolic pathways.

Sulfated molecules with diverse functions are common in biology, but sulfonation as a method to activate a metabolite for chemical catalysis is rare. Catalytic activity was characterized and crystal structures were determined for two such "activating" sulfotransferases (STs) that sulfonate β-hydroxyacyl thioester substrates. The CurM polyketide synthase (PKS) ST domain from the curacin A biosynthetic pathway of Moorea producens and the olefin synthase (OLS) ST from a hydrocarbon-producing system of Synechococcus PCC 7002 both occur as a unique acyl carrier protein (ACP), ST, and thioesterase (TE) tridomain within a larger polypeptide.

Characterization of molecular interactions between ACP and halogenase domains in the Curacin A polyketide synthase.

Polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs) are large multidomain proteins present in microorganisms that produce bioactive compounds. Curacin A is such a bioactive compound with potent anti-proliferative activity. During its biosynthesis the growing substrate is bound covalently to an acyl carrier protein (ACP) that is able to access catalytic sites of neighboring domains for chain elongation and modification.

The unique mechanistic transformations involved in the biosynthesis of modular natural products from marine cyanobacteria.

Cyanobacteria are abundant producers of natural products well recognized for their bioactivity and utility in drug discovery and biotechnology applications. In the last decade, characterization of several modular gene clusters that code for the biosynthesis of these compounds has revealed a number of unusual enzymatic reactions. In this article, we review several mechanistic transformations identified in marine cyanobacterial biosynthetic pathways, with an emphasis on modular polyketide synthase(PKS)/non-ribosomal peptide synthetase (NRPS) gene clusters.