Biosynthèse des dérivés triphosphorylés de la thiamine chez E. coli

Doctoral thesis (2012)

La biosynthèse des lipopolysaccarides chez Escherichia coli

Scientific conference (2011, February 25)

Biosynthesis of 5-aminolevulinic acid via the Shemin pathway in a green sugar beet callus

in Biologia Plantarum (1998), 40(4), 493-497

5-Aminolevulinic acid synthase (ALAS) has been detected in a normal (auxin- and cytokinin-dependent) green sugar beet callus under light and under darkness. ALAS activity was lower when the callus was ... [more ▼]

5-Aminolevulinic acid synthase (ALAS) has been detected in a normal (auxin- and cytokinin-dependent) green sugar beet callus under light and under darkness. ALAS activity was lower when the callus was grown under light. The supply of precursors of the Shemin pathway (glycine and succinate) to dark-grown callus enhanced considerably the capacity of the 5-aminolevulinic acid (ALA) formation. Glutamate, gamma-aminobutyrate or a-ketoglutarate also increased ALA accumulation. Such an accumulation was also obtained after inhibition of polyamine synthesis. The results show that glutamate or its derivatives might feed the Shemin pathway in conditions preventing glutamate to be used through the Beale pathway. [less ▲]

Biosynthesis of defensive compounds from beetles and ants

in European Journal of Organic Chemistry (2003), 15

Many beetle and ant species owe their protection against predators to the presence of defensive compounds in their hemolymph or in specialized exocrine glands. A growing number of studies devoted to the ... [more ▼]

Many beetle and ant species owe their protection against predators to the presence of defensive compounds in their hemolymph or in specialized exocrine glands. A growing number of studies devoted to the elucidation of the biosynthetic pathways used by the insects to produce these compounds have been reported in recent years. An over-view of these studies is presented. [less ▲]

Biosynthesis of peroxidases: a role as interplay between primary and hormonal metabolisms

in Acosta, M.; Rodriguez-lopez, J.-N.; Pedreno, Maria-A (Eds.) Plant perodixases - Biochemistry and physiology - VI international plant peroxidase symposium Proceedings (2002)

Hyperhydric, fully habituated (growth independent from exogenous auxin and cytokinin), fully heterotrophic (achlorophyllous, dependent on sucrose supply, nevertheless able to fix CO2 non ... [more ▼]

Hyperhydric, fully habituated (growth independent from exogenous auxin and cytokinin), fully heterotrophic (achlorophyllous, dependent on sucrose supply, nevertheless able to fix CO2 non-photosynthetically) and non-organogenic (complete loss of any organogenic totipotency) sugarbeet cells in culture were characterized by a very low peroxidase activity, among other deficient heme compounds. This deficiency resulted from the lack of synthesis of the precursor aminolevulinic acid (ALA) through the chloroplastic Beale pathway; the low productive unusual ALA synthesis through the mitochondrial Shemin pathway (commonly used by animals and fungi) functioned but further at a limited rate due to inhibition of ALA-dehydratase by benzoic derivatives, predominant among the phenolic acids of these cells (compared to normal ones). A thorough investigation of the metabolic and hormonal functioning of these neoplastic cells showed that the above deviation originated from a disturbed nitrogen metabolism that diverted glutamate from the Kreb's cycle into polyamine (over) synthesis, which had also as consequence a low ethylene production. The Kreb's cycle could be replenished by oxaloacetate and malate deriving from the anaplerotic fixation of CO2 onto phosphoenolpyruvate. A privileged pentose phosphate pathway (PPP) allowed the formation of substrates for a non-limited biosynthesis of (endogenous) auxins and cytokinins. The PPP, through NAD(P)H formation, enhanced nitrogen metabolism, but also, together with a putative H2O2 accumulation (originated from high superoxide dismutase activity and high polyamine oxidation combined with low catalase activity), favoured the alternative respiratory pathway. These results not only illustrate a novel view of integration of hormonal metabolisms with the C and N primary and secondary ones but also allow to consider the biosynthesis of peroxidases in an interplay or mediating role between them. [less ▲]

Biosynthesis of type IV and V (alpha A-alpha B) collagens by human placenta.

in Collagen and Related Research (1981), 1(2), 137-50

The collagenous proteins synthesized by placenta in organ culture were characterized. Types I and III collagen accounted for about two-thirds of the collagenous protein produced by the tissue while type ... [more ▼]

The collagenous proteins synthesized by placenta in organ culture were characterized. Types I and III collagen accounted for about two-thirds of the collagenous protein produced by the tissue while type IV procollagen comprised around 10%. Type IV collagen contained two chains of 185,000 and 175,000 daltons which are genetically distinct from one another as determined by a peptide mapping procedure. The type IV procollagen was identical to that produced by other tissues based on ratios of 3- to 4-hydroxyproline and hydroxyproline to proline, and on the pattern produced upon polyacrylamide gel electrophoresis before and after peptide mapping procedures. About 20% of the collagen resembled type V collagen in the proportions of 3- and 4-hydroxyproline to proline and of hydroxylysine to lysine, in solubility, and in peptide maps. However, it contained disulfide linked chains larger than those found in the type V collagen solubilized by pepsin. Following pepsin treatment, the disulfide bonds were removed and the mobility of the chains of the labeled protein resembled those in type V collagen. It is likely that the disulfide linked protein represents the intact type V collagen molecule. [less ▲]

Biosynthetic studies on adaline and adalinine, two alkaloids from ladybird beetles (Coleoptera : Coccinellidae)

in Tetrahedron (2001), 57(16), 3403-3412

The biosynthesis of the homotropane alkaloid (-)-adaline in the coccinellid beetle Adalia bipunctata has been studied by incorporation experiments with [1-C-14] and [2-C-14]acetate. A degradation scheme ... [more ▼]

The biosynthesis of the homotropane alkaloid (-)-adaline in the coccinellid beetle Adalia bipunctata has been studied by incorporation experiments with [1-C-14] and [2-C-14]acetate. A degradation scheme was developed which selectively afforded benzoic acid containing the carbonyl carbon atom of adaline. The labelling pattern thus obtained indicated that the alkaloid is biosynthesized via a polyacetate pathway. Moreover, feeding A. bipunctata adults with (-)-[10,10,11,11,12,12,13,13,14,14,14-H-2(11)]adaline . HCl afforded (-)-[7,7,8,8,9,9,10,10,11,11,11-H-2(11)]adalinine, demonstrating a biogenetic relationship between the two alkaloids. possible mechanisms for this conversion are discussed. Finally, the synthetic scheme devised to obtain (+/-)-6-acetonyl-2-pentyl-1-piperideine did not yield the target compound, but afforded instead (+/-)-adaline in moderate yields. This unexpected result gives support to the hypothesis that this piperideine could be a key intermediate in the biosynthesis of adaline. [less ▲]

Biotechnical conversion of xylose to xylitol by Pachisolen tannophilus

Book published by Elsevier (1984)

A biotechnological process to produce sulfide from the industrial by-product gypsum : new investigations

in Med. Fac. Landbouww. Univ. Gent 60/4b (1995)

Different methods to isolate acetate-oxidizing sulfate-reducing bacteria (SRB) have been applied to samples containing relatively high concentrations of sulfate. However, the presence of facultative ... [more ▼]

Different methods to isolate acetate-oxidizing sulfate-reducing bacteria (SRB) have been applied to samples containing relatively high concentrations of sulfate. However, the presence of facultative anaerobic bacteria, identified as enterobacteriaceae, did not allow to obtain pure strains. Consequently, the influence of this contaminant in SRB cultures was investigated with particular attention being paid to the gases produced by the contaminant. [less ▲]

La Biotechnologie : un outil pour l'agro-alimentaire

in Nouvelles de la Science et des Technologies (1989), 7(2), 31-42