Selective enzymatic hydrolysis of aromatic diesters using esterase from Brevibacterium imperiale B222

Summary A practical procedure has been developed for the chemoselective microbial hydrolysis of aromatic dicarboxylic esters to give the corresponding monoesters, using cellular lysate and whole cell of Brevibacterium imperiale B222. The produced monoesters can be transformed into hydroxyacids, useful intermediates in the synthesis of polyesters.     

Intestinal transport of thiamin and thiamin monophosphate in rat everted jejunal sacs: a comparative study using some potential inhibitors

Rat everted jejunal sacs were incubated for 15 and 30 min at 37 degrees C in oxygenated Krebs-Henseleit buffer, pH 7.4, containing 0.2 microM [3H]-thiamin (3H-T) or [3H]-thiamin monophosphate (3H-TMP) with and without 10 mM 1-phenylalanine (PAL) or 2.5 mM levamisole (LEV). The concentrations of 3H-T and its phosphoesters in sac wall and serosal fluid were determined by a radiometric method after electrophoretic separation. In separate experiments, thiamin pyrophosphokinase (TPKase) and thiamin pyrophosphatase (TPPase) activities were determined in mucosal scrapings, with and without PAL or LEV, by using a radiometric and a colorimetric method, respectively. 3H-TMP was transported partly unchanged by an active mechanism similarly to 3H-T, but less efficiently. During transport, 3H-TMP was also enzymatically transformed to thiamin (T) and thiamin pyrophosphate, which accumulated in the tissue. In the serosal fluid, the concentration of 3H-TMP exceeded that of 3H-T. Presence of PAL or LEV with 3H-T or 3H-TMP in the incubation medium reduced the serosal transport and the tissue content of T compounds. LEV caused a dose-dependent inhibition of TPKase without affecting TPPase, whereas PAL inhibited both activities to about the same extent. These results indicate that the transport of TMP involves a number of different processes similar to those responsible for T transport. The effects of PAL and LEV underline the importance of phosphorylation-dephosphorylation coupling.     

GarA is an essential regulator of metabolism in Mycobacterium tuberculosis

Alpha‐ketoglutarate is a key metabolic intermediate at the crossroads of carbon and nitrogen metabolism, whose fate is tightly regulated. In mycobacteria the protein GarA regulates the tricarboxylic acid cycle and glutamate synthesis by direct binding and regulation of three enzymes that use α‐ketoglutarate. GarA, in turn, is thought to be regulated via phosphorylation by protein kinase G and other kinases. We have investigated the requirement for GarA for metabolic regulation during growth in vitro and in macrophages. GarA was found to be essential to Mycobacterium tuberculosis, but dispensable in non‐pathogenic Mycobacterium smegmatis. Disruption of garA caused a distinctive, nutrient‐dependent phenotype, fitting with its proposed role in regulating glutamate metabolism. The data underline the importance of the TCA cycle and the balance with glutamate synthesis in M. tuberculosis and reveal vulnerability to disruption of these pathways.     

Astrocyte–neuron interactions in neurological disorders

Astrocytes have long been considered as just providing trophic support for neurons in the central nervous system, but recently several studies have highlighted their importance in many functions such as neurotransmission, metabolite and electrolyte homeostasis, cell signaling, inflammation, and synapse modulation. Astrocytes are, in fact, part of a bidirectional crosstalk with neurons. Moreover, increasing evidence is stressing the emerging role of astrocyte dysfunction in the pathophysiology of neurological disorders, including neurodegenerative disease, stroke, epilepsy, migraine, and neuroinflammatory diseases.     

Restriction of the T-cell receptor V delta gene repertoire is due to preferential rearrangement and is independent of antigen selection

To determine whether the limited V gene usage by the T-cell receptor delta (TCRD) chain is dictated by preferential rearrangement or by antigen selection, we characterized and compared the TCRDV gene repertoire of the productive with that of the unprotective allele in 80 human TCRG/TCRD clones. Six different V genes were found on the expressed allele; two of them, provisionally named DV7 and DV8, have not been described before on the surface of TCRG/TCRD T cells. Overall, six V genes and six non-V elements were isolated from the unproductive allele. Interestingly, the same set of genes was rearranged both in the productive and in the unproductive chromosome. These findings seem to suggest that antigen-independent mechanisms play a major role in the restriction of the TCRDV gene repertoire.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide database and have been assigned the accession numbers Z46643 (DV7-E2), Z46644 (DV8-E6), Z46645 (DV8-M1), Z46641 (AV12-E4), Z46642 (AV29-E5), Z46652 (DREC-E13), Z46637 (TCR-d), Z46638 (TCR-n), Z46639 (TCR-r), Z46653 (PSI-DVu), and Z46640 (TCR-w)