棒束孢霉胞外多糖的纯化

棒束孢霉发酵上清液经减压浓缩、醇析、蛋白酶法与Ｓｅｖａｇ法结合脱蛋白、逆向流水透析和ＤＥＡＥ－ＳｅｐｈａｄｅｘＡ－５０柱层析等步骤，获得了胞外纯多糖。用ＴＬＣ、ＧＣ及ＩＲ分析表明，该多糖链由Ｄ－甘露醇和Ｄ－半乳糖组成。     

Complete mineralization of methylparathion by Pseudomonas sp. A3

Organophosphorus insecticides are widely used in agriculture. Despite their biodegradable nature, some are highly toxic and their residues are found in the environment. Reports on the mineralization of a spectrum of these insecticides by a single potential strain are scarce. We have isolated a soil isolate, Pseudomonas sp. A3, through enrichment technique, able to degrade methylparathion (MP), malathion, monocrotophos, and Diazinon. The potential of this strain to mineralize MP as a carbon and/or phosphorus source has been evaluated. On hydrolysis of MP, the aromatic portion (p-nitrophenol) was used as a carbon and energy source whereas the alkyl moiety (dithiomethylphosphorothioate) was broken down for the phosphorus source. The results from the experiments involving [U-¹⁴C]p-nitrophenol provided the evidence for incorporation of carbon into the cellular constituents and release of CO₂ from this insecticide. During the breakdown of MP, nitrite was released as a catabolic by-product.     

Structure and Function of a Multidomain Alkaline Xylanase from Alkaliphilic Bacillus Sp. Strain 41M-1

Xylanase is an enzyme that catalyzes the hydrolysis of xylan, a -1,4-linked xylose polymer. Alkaliphilic Bacillus sp. strain 41M-1 secretes a xylanase (xylanase J) that has an alkaline pH optimum. Xylanase J is a multidomain enzyme and consists of two functional domains: a family 11/G catalytic domain and a non-catalytic xylan-binding domain. The xylan-binding domain bound to xylan and enhanced catalytic activity of the adjacent catalytic domain. Mutational analyses revealed some amino acid residues that contribute to catalytic activity, alkaliphily and xylan-binding activity of xylanase J.     

Submerged culture screening of two strains ofStreptomyces sp. with high keratinolytic activity

Keratinases can be used for the production of potentially important hydrolyzed proteins and chemicals. This study investigated the keratinolytic activity ofStreptomyces sp on keratinaceous materials like wool. High levels of proteolytic and keratinolytic activity were obtained after 96 h of culture when two Streptomyces sp strains were grown on basal medium containing mineral salts and 3% (w/v) of defatted wool as a source of energy, carbon, and nitrogen. The cell-free culture filtrates exhibited rapid proteolytic digestion of keratin powder. Currently, the authors are testing whether the enzymatic activity obtained is in fact keratinolytic, and not only an alkaline protease activity.     

Belamide A, a new antimitotic tetrapeptide from a Panamanian marine cyanobacterium

The isolation and structure elucidation of belamide A from the marine cyanobacterium Symploca sp. is described. Belamide A is a highly methylated linear tetrapeptide with structural analogy to the important linear peptides dolastatins 10 and 15. Disruption of the microtubule network in A-10 cells was observed at 20 μM and displayed classic tubulin destabilizing antimitotic characteristics. The moderate cytotoxicity of belamide A (IC₅₀ 0.74 μM vs HCT-116 colon cancer line) provides new insights into structure-activity relationships for this drug class.     

Lissoclibadin 1, a novel trimeric sulfur-bridged dopamine derivative, from the tropical ascidian Lissoclinum cf. badium

A novel tribenzotetrathiepin alkaloid, named lissoclibadin 1 (1), has been isolated from the ascidian Lissoclinum sp. (cf. L. badium Monniot and Monniot, 1996). The gross structure was assigned on the basis of the spectral data, and one of two possible isomers was selected by the computational modeling study. Lissoclibadin 1 inhibited the growth of the marine bacterium Ruegeria atlantica (15.2 mm at 20 μg/disk).     

Aspergilolide,a steroid lactone produced by an endophytic fungus Aspergillus sp. MBL1612 isolated from Paeonia ostii

A new steroid lactone aspergilolide (1), and nine known compounds helvolic acid (2), verruculogen (3), tryprostatin B (4), 13-oxofumitremorgin B (5), fumitremorgin C (6), demethoxy fumitremorgin C (7), terezine D (8), aszonalenin (9), 12, 13-dihydroxy-fumitremorgin C (10) from cultures of the endophytic fungus Aspergillus sp. MBL1612. Their chemical structures were determined by a series of extensive spectroscopic methods. All of the compounds were isolated from this genus for the first time. The cytotoxicity against five human cancer cell lines of new compound were detected.     

A rare diketopiperazine glycoside from marine-sourced Streptomyces sp. ZZ446

Abstract

Two diketopiperazines were isolated from a culture of the marine-derived actinomycete Streptomyces sp. ZZ446. Their structures were elucidated as maculosin (1) and maculosin-O-α-L-rhamnopyranoside (2) based on their NMR and HRESIMS data, specific rotation, and chemical degradation. Maculosin-O-α-L-rhamnopyranoside (2) is a new diketopiperazine glycoside, a structural class not reported previously from the natural sources. Both compounds showed antimicrobial activity against methicillin-resistant Staphylococcus aureus, Escherichia coli, and Candida albicans with MIC values in a range from 26.0 to 37.0?μg/mL.

     

Kadsutherins A–C: Three New Dibenzocyclooctane Lignans from the Stems of Kadsura Species

Three new dibenzocyclooctane‐type lignans, kadsutherins A–C ( 1 – 3 ), were isolated from the stems of two Kadsura species. Their structures and configurations were elucidated by spectroscopic methods including 2D‐NMR and HR‐MS techniques. Kadsutherin C ( 3 ) is the first dibenzocyclooctane lignan without an oxygen‐containing substituent at C(2).     

Purification, characterization, and structural investigation of a new moderately thermophilic and partially calcium-independent extracellular α-amylase from Bacillus sp. TM1

A new α-amylase was extracted from a recently found strain of Bacillus sp. and purified by ion-exchange chromatography. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed a single band for the purified enzyme with an apparent molecular weight of 59 kDa. The optimum temperature and pH range of the enzyme were 40–60°C and 4.5–7.5, respectively, and its activation energy was 1.974 kcal/mol. The K _m value for the enzyme activity on solubie starch was 4 mg/mL, and the T _m values obtained from the circular dichroism (CD) results of thermal unfolding were 78.7 and 80.2°C in the absence and presence of the calcium, respectively. The enzyme was almost completely inhibited by the addition of Fe³⁺, Mn²⁺, and Zn²⁺ and was activated by EDTA, Cr³⁺, and Al³⁺. Moreover, it was partially inhibited by Ca²⁺, Ba²⁺, Ni²⁺, and Co²⁺. Proteolytic digestion of the enzyme using trypsin combined with results from T _m using CD and irreversible thermoinactivation suggests that this enzyme can be considered a moderate thermophile with both mild flexibility and rigidity.