Isolation of S-adenosyl-L-methionine from an enriched Kluyveromyces lactis mutant,grown in whey media

The ability of six lactose-digesting yeast strains to accumulate S-adenosyl-L-methionine (AdoMet) when grown on whey medium was studied. Kluyveromyces lactis ATCC 8585 accumulated the greatest amount of AdoMet (15.2 mg per gram biomass) and was chosen for the development of an Ado-Met-enriched mutant. The Ado-Met-enriched mutant AM-65 was selected from mutants induced with N-methyl-N-nitro-N'-nitrosoguanidine. The strain accumulated 61.6 mg AdoMet per gram biomass. The effect of concentrations of medium components on AdoMet biosynthesis was studied. The ability of the mutant to accumulate AdoMet remained stable after multiple reinoculations.     

Penicillin amidase-catalysed preparative synthesis of cephem - 7- (2-benzoxazolon-3-yl-acetamido)-desacetoxycephalosporanic acid using a non-specific polyethyleneglycol-modified acyl donor

Summary Penicillin amidase (EC 3.5.1.11) catalysed the synthesis of cephem 7-(2-benzoxazolon-3-yl-acetamido)-desacetoxycephalosporanic acid by a kinetically controlled transfer of the non-specific 2-benzoxazolon-3-yl-acetyl moiety from its polyethyleneglycol ester (m.w. 400, nine monomeric units) to the nucleophile 7-aminodesacetoxycephalosporanic acid. Penicillin amidase from E.Coli immobilised in polyacrylamide gel was used as biocatalyst. A high degree of nucleophile conversion (98 %) into the corresponding cephem at biotechnologically relevant concentrations (50 mM) was achieved.     

QSAR study and synthesis of new phenyltropanes as ligands of the dopamine transporter (DAT)

The dopamine transporter (DAT) plays a pivotal role in the regulation of dopamine neurotransmission, and is involved in a number of physiological functions and brain disorders. Furthermore the DAT analysis by molecular imaging techniques is a useful tool for the diagnosis and follow up treatment of diseases involving the DAT. In order to predict the affinity of new derivatives for the DAT, different QSAR molecular modeling models based on cocaine were compared. We have evaluated in these models tropane derivatives synthesized with original synthons which coupled properties of both fluorine and iodine atoms. One compound showed a high in vitro affinity and selectivity for the DAT (K(i)=0.87±0.04 nM). This compound should be radiolabeled with radioiodine for further investigations by SPECT.     

Fosmidomycin analogues as inhibitors of monoterpenoid indole alkaloid production in Catharanthus roseus cells

Substituted 3-[2-(diethoxyphosphoryl)propyl]oxazolo[4,5-b]pyridine-2(3H)-ones were obtained by functionalization at 6-position with various substituents (aryl, vinyl, carbonyl chains) via reactions catalysed with palladium. We found that these new fosmidomycin analogues inhibited the accumulation of ajmalicine, a marker of monoterpenoid indole alkaloids production in plant cells. Some of them have greater inhibitory effect than fosmidomycin and fully inhibit alkaloid accumulation at the concentration of 100 microM.     

Synthesis and biological evaluation with plant cells of new fosmidomycin analogues containing a benzoxazolone or oxazolopyridinone ring

Fosmidomycin, 3-(N-formyl-N-hydroxyamido) propylphosphonic acid sodium salt, is an efficient inhibitor of 1-deoxy-D-xylulose-5-phosphate (DOXP) reductoisomerase, the second enzyme of the 2C-methyl-D-erythritol-4-phosphate (MEP) pathway notably present in Plasmodium species. We have synthesized a new series of analogues of fosmidomycin, containing a benzoxazolone, benzoxazolethione or oxazolopyridinone ring. As the MEP pathway is involved in the biosynthesis of all isoprenoids, accumulation of ajmalicine in Catharanthus roseus cells was chosen as a marker of monoterpenoid indole alkaloid (MIA) production. None of the twelve studied phosphonic esters 3 and phosphonic acids 4 affected periwinkle cell growth, but some of them (3c, 3e, 3g and 3h) showed a significant inhibition of ajmalicine accumulation: 45-85% at 125 microM. Surprisingly, this effect disappeared by conversion of 3c and 3g into the corresponding acids 4c and 4g, respectively.     

One-pot synthesis of functionalized 4,5-dihydroisoxazole derivatives via nitrile oxides and biological evaluation with plant cells

1,3 Dipolar cycloadditions of nitrile oxides generated in situ in the presence of a variety of olefins provided 4,5-dihydroisoxazoles. The whole procedure could be performed in a practical and efficient one-pot operation. The products are of excellent purity (95%) and are isolated in 60-83% yields. Some of them enhanced the accumulation of indole alkaloids in periwinkle cell cultures.     

Pbx4, a new Pbx family member on mouse chromosome 8, is expressed during spermatogenesis

Members of the Pbx family are involved in a diverse range of developmental processes including axial patterning and organogenesis. Pbx functions are in part mediated by the interaction of Pbx proteins with members of the Hox and Meis/Prep families. We have identified a fourth mammalian Pbx family member. Pbx4 in the mouse and PBX4 in humans are located on chromosome 8 and chromosome 19, respectively. Pbx4 expression is confined to the testis, especially to spermatocytes in the pachytene stage of the first meiotic prophase.     

Oscillations in Biochemical Reaction Networks Arising from Pairs of Subnetworks

Biochemical reaction models show a variety of dynamical behaviors, such as stable steady states, multistability, and oscillations. Biochemical reaction networks with generalized mass action kinetics are represented as directed bipartite graphs with nodes for species and reactions. The bipartite graph of a biochemical reaction network usually contains at least one cycle, i.e., a sequence of nodes and directed edges which starts and ends at the same species node. Cycles can be positive or negative, and it has been shown that oscillations can arise as a result of either a positive cycle or a negative cycle. In earlier work it was shown that oscillations associated with a positive cycle can arise from subnetworks with an odd number of positive cycles. In this article we formulate a similar graph-theoretic condition, which generalizes the negative cycle condition for oscillations. This new graph-theoretic condition for oscillations involves pairs of subnetworks with an even number of positive cycles. An example of a calcium reaction network with generalized mass action kinetics is discussed in detail.