[en] A two-step protocol for the synthesis of 15-alkylidene and benzylidene derivatives of 14-deoxy-11,12-didehydroandrographolide, which was conducted through a dehydration reaction of andrographolide and a vinylogous aldol condensation between α,β-unsaturated butenolide moiety and benzaldehyde derivatives has been developed. Combining with various experiments on new catalysts for these reactions: the dehydration of andrographolide by concentrated H₂SO₄ and the vinylogous aldol reaction by K₂CO₃ in MeOH or a mixture of CH₃COOH/pyrrolidine in MeOH, this research has determined the optimized conditions for those catalysts and the new approach to this aldol-like reaction. All compounds synthesized were characterized by the analysis of IR, NMR, HRMS spectra. (author)

[en] The two converging catechol and protocatechuate branches of the β-ketoadipate pathway in Pseudomonas putida have long been considered a paradigm of evolutionary divergence of specialized enzymes from a common ancestor. The structural similarities of substrates, products and the enzymes themselves have supported this hypothesis. Employing chemical and ¹H NMR techniques, they have determined the absolute stereochemical courses of the reactions catalyzed by β-carboxymuconate cycloisomerase, muconolactone isomerase, and γ-carboxymuconolactone decarboxylase. Surprisingly, β-carboxymuconate cycloisomerase proceeds via an anti addition while the corresponding muconate cycloisomerase has been shown to catalyze a syn addition. Moreover, the chiral centers generated in the products of both enzymes are of the opposite relative configuration. They believe that the shift in mechanism may reflect basic energetic differences of the two reactions. The stereochemistries of the isomerase and decarboxylase have been established by ¹H NMR using a ricochet analysis. Both reactions proceed via a syn process; the relative configurations of muconolactone and γ-carboxymuconolactone necessitate that the enzymes operate on opposite faces of the common enol-lactone product. These findings suggest that either critical active site changes have occurred in these enzymes to accommodate preferred mechanistic pathways or the evolutionary relationship of the two branches is more remote than previously believed

No abstract available

[en] Cotton fibers are unicellular seed trichomes and the largest known plant cells. Fiber morphogenesis in cotton is a complex process involving a large number of genes expressed throughout fiber development process. The expression profiling of five gene families in various cotton tissues was carried out through real time PCR. Expression analysis revealed that transcripts of expansin, tubulin and E6 were elevated from 5 to 20 days post anthesis (DPA) fibers. Three Lipid transfer proteins (LTPs) including LTP1, LTP3, LTP7 exhibited highest expression in 10 - 20 DPA fibers. Transcripts of LTP3 were detected in fibers and non fiber tissues that of LTP7 were almost negligible in non fiber tissues. Sucrose phosphate synthase gene showed highest expression in 10 DPA fibers while sucrose synthse (susy) expressed at higher rate in 5-20 DPA fibers as well as roots. The results reveal that most of fiber related genes showed high expression in 5-20 DPA fibers. Comprehensive expression study may help to determine tissue and stage specificity of genes under study. The study may also help to explore complex process of fiber development and understand the role of these genes in fiber development process. Highly expressed genes in fibers may be transformed in cotton for improvement of fiber quality traits. Genes that were expressed specifically in fibers or other tissues could be used for isolation of upstream regulatory sequences. (author)

No abstract available

[en] Incubation of 3-d-old seedlings of Oryza sativa L. cv Arborio under anaerobic conditions, leads to a large increase in the titer of free putrescine while aerobic incubation causes a slight decrease. After 2 days, the putrescine level is about 2.5 times greater without oxygen than in air. The rice coleoptile also accumulates a large amount of bound putrescine and, to a lesser extent, spermidine and spermine (mainly as acid-soluble conjugates). Accumulation of conjugates in the roots is severely inhibited by the anaerobic treatment. Feeding experiments with labeled amino acids showed that anoxia stimulates the release of ¹⁴CO₂ from tissues fed with [¹⁴C]arginine and that arginine is the precursor in putrescine biosynthesis. After 2 d of anoxia, the activity of arginine decarboxylase was 42% and 89% greater in coleoptile and root, respectively, than in the aerobic condition. The causes of the differences in polyamine metabolism in anoxic coleoptiles and roots are discussed

[en] In Selenomoans ruminantium, a strictly anaerobic and gram negative bacterium, cadaverine and putrescine are the essential constituents of its peptidoglycan. S. ruminantium does not contain both free and bound types of lipoprotein, but it contains cadaverine as a component of its peptidoglycan. S-adenosylmethionine decarboxylase (SAMDC) is a key enzyme for a synthesis of spermidine and spermine in S. ruminantium. The crude extract of S. ruminantium was preincubated at 100 degrees Celcius and its SAMDC activity was measured by using a "1"4C labeled substrate. We report here on a heat stable SAMDC which is able to withstand a temperature up to 100 degrees Celcius

No abstract available

[en] α-Amino-β-carboxymuconate-ϵ-semialdehyde decarboxylase (ACMSD) plays an important role in L-tryptophan degradation via the kynurenine pathway. ACMSD forms a homodimer and is functionally inactive as a monomer because its catalytic assembly requires an arginine residue from a neighboring subunit. However, how the oligomeric state and self-association of ACMSD are controlled in solution remains unexplored. In this study, we demonstrate that ACMSD from Pseudomonas fluorescens can self-assemble into homodimer, tetramer, and higher-order structures. Using size-exclusion chromatography coupled with small-angle X-ray scattering (SEC-SAXS) analysis, we investigated the ACMSD tetramer structure, and fitting the SAXS data with X-ray crystal structures of the monomeric component, we could generate a pseudo-atomic structure of the tetramer. This analysis revealed a tetramer model of ACMSD as a head-on dimer of dimers. We observed that the tetramer is catalytically more active than the dimer and is in equilibrium with the monomer and dimer. Substituting a critical residue of the dimer–dimer interface, His-110, altered the tetramer dissociation profile by increasing the higher-order oligomer portion in solution without changing the X-ray crystal structure. ACMSD self-association was affected by pH, ionic strength, and other electrostatic interactions. Alignment of ACMSD sequences revealed that His-110 is highly conserved in a few bacteria that utilize nitrobenzoic acid as a sole source of carbon and energy, suggesting a dedicated functional role of ACMSD's self-assembly into the tetrameric and higher-order structures. Finally, these results indicate that the dynamic oligomerization status potentially regulates ACMSD activity and that SEC-SAXS coupled with X-ray crystallography is a powerful tool for studying protein self-association.

[en] The result indicates that Z-enolates are formed stereose-lectively from AHA derivatives by the chelation-controlled reaction and that the regiochemistry of the enolates from the AHA derivatives can be controlled by the simple choice of the appropriate protecting group for the amino group. Further studies are underway to explore the catalytic asymmetric synthesis of aminoketose sugars from AHA derivatives. 1-Amino-3-hydroxyacetone is the deoxyamino-derivative of 1,3-dihydroxyacetone. Nature utilizes dihydroxyacetone phosphate, a phosphorylated form of DHA, as the donor substrate in enzymatic aldol reactions for the synthesis of ketose sugars. Although DHAP-dependent aldolases possess an almost perfect ability to control the stereochemistry of aldol products, they are relatively unstable and do not accept many useful aldehydes as acceptor substrates. The chemical aldol reaction of protected DHAs with aldehydes, therefore, attracted a great deal of attention as a useful supplement or alternative to the enzymatic aldol reaction of DHAP. Since the first report on the chemical aldol reaction of protected DHAs with aldehydes by our laboratory, there have been numerous reports on diastereoselective and enantioselective aldol reactions of DHA derivatives with various aldehydes. Consequently, the DHA unit is now well recognized as a versatile C₃ building block in organic synthesis