Catálogo de publicaciones - libros

Besides metabolic pathways and regulatory networks, transport reactions are also pivotal for understanding amino acid metabolism and production in bacteria. Apart from substrate uptake, this refers to product (amino acid) excretion as well as product re-uptake. Both the mechanistic (kinetic and energetic) as well as structural properties of these transport systems are relevant for understanding their significance and for providing a basis for rational metabolic design. Transport systems have been classified into numerous different carrier families, according to their structural properties and their putative evolutionary relation. The diversity of amino acid uptake and excretion systems in two biotechnologically relevant organisms, namely K12 and ATCC 13032 is described in this review on the basis of their relation to these different transporter families. Particular functional and molecular properties of specific amino acid excretion systems in these two organisms, in particular those responsible for efflux of lysine (and arginine), threonine, branched chain amino acids, cysteine (and cysteine derivatives) and glutamate are described. A complete list of all secondary and primary transport systems in putatively related to amino acid transport is provided.

l-α-Dipeptides are not mere mixtures of amino acids. Some of them have their own properties which are not found in the corresponding amino acids. Despite such versatility, dipeptides have been poorly recognized, mainly due to the lack of an efficient manufacturing method. Though a variety of dipeptides, many of which contain unusual amino acids or have a cyclic form, have been found as metabolites of microorganisms, their biosynthetic routes had remained unclear. However, recent studies have revealed the existence of several ribosome-independent machineries capable of synthesizing dipeptides, such as nonribosomal peptide synthetases or the new enzyme, l-amino acid α-ligase . By using these activities, highly efficient methods for producing dipeptides have been devised. In this review, known functions and occurrence of dipeptides are reviewed first since many readers may not be familiar with dipeptides. Then a few important studies on the biosynthesis of dipeptides are summarized followed by a description of the emerging technologies for dipeptide manufacturing based on the recent findings.

The complete nucleotide sequence of the genomes of several strains of and reveal the genetic blueprint of these industrial organisms including their structural genetic organization and their metabolic networks and conversion capabilities, refine the understanding of their phylogenetic positions, and open the possibility to assess the expected size of their pan-genomes in order to harness their diversity. The genome of R codes for approximately 3000 genes, a minimum of 5.3% of which are related to amino acid transport and metabolism and 4.6% to carbohydrate transport and metabolism. The genome of K-12 encodes approximately 4450 genes, 7.5% of which are involved in amino acid transport and metabolism and 6.1% in carbohydrate transport and metabolism. Global techniques were enabled by these complete genomic sequences, including analyses by global transcription profiling, proteomics and metabolomics to gather biological data, and megabase molecular biology tools to engineer at will these organisms at various scales, from the level of single base pairs to that of chromosomes. Systems biology represents the next technological paradigm necessary on the one hand to efficiently integrate and process the large volume of global biological information thus attained, in order to understand bacterial physiology and organization at a higher level; and on the other hand to enable in silico models useful for generating optimization strategies of increasing complexity and relevance, in the hope to lead faster towards improved metabolic engineering solutions with the aim of attaining expanded industrial process scope and superior economics.