Serine hydroxymethyltransferase from the silkworm Bombyx mori: Identification, distribution, and biochemical characterization.

Serine hydroxymethyltransferase (SHMT) catalyzes the interconversion of serine and tetrahydrofolate (THF) to glycine and methylenetetrahydrofolate. cDNA encoding Bombyx mori SHMT (bmSHMT) was cloned and sequenced. The deduced amino acid sequence consisted of 465 amino acids and was found to share homology with other SHMTs. Recombinant bmSHMT was overexpressed in Escherichia coli and purified to homogeneity. The enzyme showed optimum activity at pH 3.0 and 30°C and was stable under acidic conditions. The Km and kcat /Km values for THF in the presence of Nicotinamide adenine dinucleotide phosphate (NADP+ ) were 0.055 mM and 0.081 mM-1 s-1 , respectively, whereas those toward NADP+ were 0.16 mM and 0.018 mM-1 s-1 and toward l-serine were 1.8 mM and 0.0022 mM-1 s-1 , respectively. Mutagenesis experiments revealed that His119, His132, and His135 are important for enzymatic activity. Our results provide insight into the roles and regulation mechanism of one-carbon metabolism in the silkworm B. mori.

Molecular characterization and expression analysis of a phosphoserine aminotransferase involving l-serine synthesis from silkworm, Bombyx mori.

In this study, we identified and characterized a phosphoserine aminotransferase (bmPSAT) from Bombyx mori (B. mori) that is responsible for l-serine biosynthesis. A complementary DNA that encodes bmPSAT was cloned by reverse transcriptase polymerase reaction and sequenced. The presumed amino acid sequence revealed 47-87% identity with known PSATs from insects, humans, plants, and bacteria. Through phylogenetic analysis, we found that bmPSAT is evolutionary related to insect PSATs. Recombinant bmPSAT was produced in Escherichia coli by using a cold-shock promotor and purified to homogeneity. This enzyme utilizes phosphohydroxypyruvate and glutamate for transamination. bmPSAT messenger RNA (mRNA) was expressed at higher levels in several tissues of standard strain silkworm including the silk gland, whereas a sericin-deficient silkworm strain exhibited a diminished expression of bmPSAT mRNA in the silk gland. These findings indicate that bmPSAT may play an important role in synthesizing and supplying l-serine in the larva of B. mori.

A novel small-molecule inhibitor of IL-6 signalling.

A small library of pyrrolidinesulphonylaryl molecules has been synthesized via an efficient 4-step route, and members evaluated for their ability to inhibit IL-6 signalling. One molecule (6a) was found to have promising activity against IL-6/STAT3 signalling at the low micromolar level, and to selectively inhibit phosphorylation of STAT3 (but not STAT1) in IL-6 stimulated MDA-MB-231 breast cancer and HeLa cell lines. It was also selectively cytostatic in MDA-MB-231 (STAT3-dependent) versus A4 (STAT3-null) cells suggesting STAT3-specific inhibitory properties.

Molecular structure of a 5,10-methylenetetrahydrofolate dehydrogenase from the silkworm Bombyx mori.

The enzyme 5,10-methylenetetrahydrofolate dehydrogenase (MTHFD) is essential for the production of certain amino acids (glycine, serine, and methionine) and nucleic acids (thymidylate and purine). Here, we identified a cDNA encoding this enzyme from the silkworm Bombyx mori. The recombinant B. mori MTHFD (bmMTHFD) expressed in Escherichia coli recognized 5,10-methylenetetrahydrofolate and 5,10-methenyltetrahydrofolate as substrate in the presence of NADP + as well as NAD +. The bmMTHFD structure was determined at a resolution of 1.75 Å by X-ray crystallography. Site-directed mutagenesis indicated that the amino acid residue Tyr49 contributed to its catalytic activity. Our findings provide insight into the mechanism underlying the activity of MTHFD from B. mori and potentially other insects and may therefore facilitate the development of inhibitors specific to MTHFD as insecticides.

Stereochenols A and B, two quinones from Stereospermum chelonoides.

Two quinones, stereochenols A (1) and B (2) were isolated from a methanol extract of the stem bark of Stereospermum chelonoides, in addition to the known naphthoquinones, sterekunthal B (3) and sterequinone C (4). The structures of these compounds were established by extensive spectroscopic analyses and by comparison of their spectral data with those of related compounds.

Facile oxidation of electron-poor benzo[b]thiophenes to the corresponding sulfones with an aqueous solution of H2O2 and P2O5.

A facile oxidation for the clean conversion of benzo[b]thiophenes to their corresponding sulfones is described employing an aqueous solution of H(2)O(2) and P(2)O(5); the solution can be prepared and stored on a multi-gram scale with a shelf-life of up to two weeks.

Phytochemical and biological investigations of methanol extract of leaves of ziziphus mauritiana lam / Investigaciones fitoquímicas y biológicas de extractos metanólicos de hojas de ziziphus mauritiana lam

Seven compounds were isolated from the methanol extract of leaves of Ziziphus mauritiana. The structures of the isolated compounds were elucidated as y-fagarine (1), beta-sitosterol (2), stigmasterol (3), alfa-amyrin (4), lupeol (5), beta-amyrin (6) and betulin (7) by extensive spectroscopic studies and by co-TLC with authentic samples. This is the first report of isolation of compounds 1-7 from this plant species. The extractives from leaves were investigated for thrombolytic, membrane stabilizing, antimicrobial, antidiarrheal and analgesic potentials along with sleep inducing property on animal model. The thrombolytic and membrane stabilizing activities were assessed by using human erythrocyte comparing with standard streptokinase and acetylsalicylic acid, respectively. The methanolic extract reduced frequency of diarrheal faeces when compared to the standard loperamide. In castor oil induced diarrhea in mice a dose dependent decrease of gastrointestinal transits were observed. In radiant heat tail-flick method the methanol extract showed moderate antinociceptive activity, compared to standard morphine.

Siete compuestos fueron aislados del extracto metanólico de hojas de Ziziphus mauritiana. Las estructuras de los compuestos aislados fueron identificadas como y-fagarina (1), beta-sitosterol (2), estigmasterol (3), alfa-amirina (4), lupeol (5), beta-amirina (6) y betulina (7 ) por medio de extensivos estudios espectroscópicos y por co-TLC con muestras auténticas. Este es el primer informe de aislamiento de los compuestos 1-7 a partir de esta especie vegetal. Los extractos de las hojas fueron investigados por efectos trombolíticos, estabilizadores de membrana, antimicrobianos, antidiarreicos y potenciales analgésicos junto a la propiedad de inducir sueño en el modelo animal. Las actividades trombolíticos y la estabilización de la membrana se evaluaron mediante el uso de eritrocitos humanos comparando con estreptoquinasa estándar y el ácido acetilsalicílico, respectivamente. El extracto metanólico redujo la frecuencia de las heces diarreicas en comparación con el estándar de loperamida. En la inducción por aceite de ricino de diarrea en ratones, se observó una disminución dosis dependiente de los tránsitos gastrointestinales. En el método del coletazo producido por calor radiante, el extracto metabólico mostró una actividad antinociceptiva moderada, en comparación con la morfina estándar.