For the ornithine fermentation pathway, described more than 70 years ago, genetic and biochemical information are still incomplete. We present here the experimental identification of the last four missing genes of this metabolic pathway. They encode L-ornithine racemase, (2R,4S)-2,4-diaminopentanoate dehydrogenase, and the two subunits of 2-amino-4-ketopentanoate thiolase. While described only for the Clostridiaceae to date, this pathway is shown to be more widespread.

[reaction: see text] Four C(11)N(5) diketopiperazine metabolites named verpacamides A (6), B (7), C (8), and D (9) consisting of a proline-arginine dipeptide skeleton have been isolated from the marine sponge Axinella vaceleti. Verpacamides A-D are a sequence of metabolites showing the transformation of proline and arginine into the oxidized guanidinyl-cyclo(Pro-Pro) 8 and 9. Compounds 6-9 are structurally and chemically related to C(11)N(5) pyrrole-2-aminoimidazole metabolites also isolated from the Axinellidae and Agelasidae families of sponges and exemplified by dispacamide A (4) and dibromophakellin (10).

New debromopyrrole-2-aminoimidazolones, debromodispacamide B (1) and debromodispacamide D (2) were isolated from the sponge Agelas mauritiana, collected in the Solomon Islands. A biomimetic one-step reaction from pseudopeptides 5 and 13 in presence of air oxygen and guanidine gave the chiral form of the natural product stereoselectively.

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Double cyclization of linear pentapeptide 3 by treatment with CsF in DMF at -5 "C gives a model bicyclic CODOE ring 2 of vancomycin in a one-pot fashion.The glycopeptide antibiotics of the vancomycin 1 (Fig. 1) family are clinically important for the treatment of infections due to methicillin-resistant Staphylococcus aureus and other gram positive organisms.' After more than 35 years of clinical use, resistance to the drug has been recently detected2 and led to renewed interests in this field. Both structural modifications of antibiotics3 and the syntheses of designed non-natural produc ts4 have appeared addressing the vancomycin resistance phenomena.The complex structure of vancomycin makes it a challenging synthetic target.5 Until now, the thallium trinitrate promoted oxidative phenolic coupling method developed by Yamamura6 and Evans7 is among the most efficient. Nevertheless, the

A new procedure for the aerobic oxidation of a-amino acids acylated by pyrrole-carboxylic acid with triplet dioxygen is introduced. The reaction is general for a variety of pyrrole-amino acid derivatives and represents a very practical and controllable method for the selective preparation of a-hydroperoxy-or a-hydroxy-a-amino acid diketopiperazines with molecular dioxygen. Furthermore, the non-catalyzed direct oxidation of amino acid derivatives at the a-position with molecular dioxygen represents a fundamental question.

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BackgroundBacteria are key components in all ecosystems. However, our knowledge of bacterial metabolism is based solely on the study of cultivated organisms which represent just a tiny fraction of microbial diversity. To access new enzymatic reactions and new or alternative pathways, we investigated bacterial metabolism through analyses of uncultivated bacterial consortia.Methodology/Principal FindingsWe applied the gene context approach to assembled sequences of the metagenome of the anaerobic digester of a municipal wastewater treatment plant, and identified a new gene which may participate in an alternative pathway of lysine fermentation.ConclusionsWe characterized a novel, unique aminotransferase that acts exclusively on Coenzyme A (CoA) esters, and proposed a variant route for lysine fermentation. Results suggest that most of the lysine fermenting organisms use this new pathway in the digester. Its presence in organisms representative of two distinct bacterial divisions indicate that it may also be present in other organisms.