Flavin-dependent halogenases (FDHs) catalyze selective halogenation of electron-rich aromatic compounds without the need for harsh oxidants required by conventional oxidative halogenation reactions. Predictive models for halogenase site selectivity could greatly improve their utility for chemical synthesis. Toward this end, we analyzed the structures and selectivity of three halogenase variants evolved to halogenate tryptamine with orthogonal selectivity.
View Article and Find Full Text PDFSymbiotic partnerships with rhizobial bacteria enable legumes to grow without nitrogen fertilizer because rhizobia convert atmospheric nitrogen gas into ammonia via nitrogenase. After Sinorhizobium meliloti penetrate the root nodules that they have elicited in Medicago truncatula, the plant produces a family of about 700 nodule cysteine-rich (NCR) peptides that guide the differentiation of endocytosed bacteria into nitrogen-fixing bacteroids. The sequences of the NCR peptides are related to the defensin class of antimicrobial peptides, but have been adapted to play symbiotic roles.
View Article and Find Full Text PDFPyruvate formate-lyase (PFL) is a glycyl radical enzyme (GRE) that converts pyruvate and coenzyme A into acetyl-CoA and formate in a reaction that is crucial to the primary metabolism of many anaerobic bacteria. The glycyl radical cofactor, which is posttranslationally installed by a radical S-adenosyl-L-methionine (SAM) activase, is a simple and effective catalyst, but is also susceptible to oxidative damage in microaerobic environments. Such damage occurs at the glycyl radical cofactor, resulting in cleaved PFL (cPFL).
View Article and Find Full Text PDFThe glycyl radical enzyme (GRE) superfamily utilizes a glycyl radical cofactor to catalyze difficult chemical reactions in a variety of anaerobic microbial metabolic pathways. Recently, a GRE, -4-hydroxy-L-proline (Hyp) dehydratase (HypD), was discovered that catalyzes the dehydration of Hyp to ()-Δ-pyrroline-5-carboxylic acid (P5C). This enzyme is abundant in the human gut microbiome and also present in prominent bacterial pathogens.
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