Uptake and Metabolism of d-Glucose by Neocosmospora vasinfecta E. F. Smith

Freshly harvested, nongrowing mycelium of Neocosmospora vasinfecta E. F. Smith rapidly absorbed exogenous glucose but converted a greater proportion to trehalose and glucan than to respiratory CO(2). This effect was accentuated in mycelium preincubated for 3.5 hours in water before exposure to glucose. Glucose was absorbed via two uptake systems, both apparently constitutive, with apparent Km values for glucose of 0.02 mm (high affinity) and 2 mm (low affinity). The glucose derivative 3-O-methylglucose (3-O-MG) was also absorbed by two apparently constitutive systems with apparent Km values for 3-O-MG of 0.065 mm and 1.9 mm. Absorption of 3-O-MG by both freshly harvested and preincubated mycelium led to its accumulation. Freshly harvested mycelium lost accumulated 3-O-MG rapidly to water, whereas preincubated mycelium showed reduced or no leakage. The reduction in leakage due to preincubation was prevented by 5 mug/ml cycloheximide in the preincubation medium. Glucose competitively inhibited 3-O-MG uptake via the high affinity system and induced loss of previously accumulated 3-O-MG from preincubated mycelium. The uptake of both glucose and 3-O-MG was associated with a transient alkalinization of the uptake medium. It is concluded that uptake of both glucose and 3-O-MG by at least the high affinity system is energy-linked and probably mediated by proton cotransport.     

Isolation,X-Ray Structure and Biological Activity of Deacetyl-dihydrobotrydial Produced by Botrytis squamosa

Mitogenic substances on human peripheral blood mononuclear leukocytes were screened from culture filtrates of microorganisms newly isolated from soil and sea water by measuring [³H]- thymidine incorporation into the cells. Strong mitogenic activity was found in marine bacteria, particularly in marine vibrios. These mitogen samples exhibited neither hemagglutinating activity nor leukoagglutinating activity. They could scarcely stimulate murine lymphocytes.

Cell-cell interaction among leukocyte subsets in response to a bacterial mitogen was investigated using the most powerfully mitogenic sample (culture filtrate of strain H 52–2). A slight decrease in the mitogen response was observed on depletion of plastic surface adherent cells. Separation of T and non-T cells from each other by erythrocyte-rosette sedimentation resulted in a markedly diminished mitogen response. Considerable restoration of the mitogen response was obtained when T cells were mixed with mitomycin C-treated adherent cells or mitomycin C-treated non-T lymphocytes, or when non-T lymphocytes were mixed with mitomycin C-treated T cells.     

Structures of Naphthoquinones Produced by the Fungus,Fusarium sp., and Their Biological Activity toward Pollen Germination

From an unidentified Fusarium sp., eight substances possessing a 1,4-naphthoquinone skeleton were isolated (F2~F9) and their structures were elucidated from the physical and chemical evidence. The effect of these compounds together with 1,4-naphthoquinone, 5-hydroxy-1,4-naphthoquinone and 5,8-dihydroxy-1,4-naphthoquinone on the pollen germination of Pinus thunbergii Pari was examined. 5,8-Dihydroxy-1,4-naphthoquinone showed marked inhibitory activity.     

Isolation and Structure of Sclerothionine,a Metabolite of Sclerotinia Fungus

A new sulfur-containing imidazole compound, m.p. 218~223°C (decomp.), ${[\alpha ]}_{\text{D}}^{24}+{7.4}^{°}$ in water), C₁₁H₁₉N₃O₃S was isolated from sclerotia of Sclerotinia libertiana and named sclerothionine. The chemical structure of sclerothionine was identified with 2-hydroxyethyl-ergothioneine which was synthesized from ethylene chlorhydrine and ergothioneine.     

Isolation and Physiological Activity of Sclerin,a Metabolite of Sclerotinia Fungus

Sclerin, a colorless crystalline, C₁₃H₁₄O₄ compound melting at 123°C was at first isolated as a lipase formation stimulating constituent of Sclerotinia libertiana, from its own mycelial extract, and infrared spectrum showed the presence a hydroxyl group and a lactone ring. Sclerin was found to promote also the enzyme formation and growth of various plant seedlings such as those of castor bean-, mung bean-, and rice seedlings. In the growth of the sclerin-treated plant, promotion of root formation and increase of dry weight per unit shoot length were noticed, and the combined use of sclerin and gibberellin brought about a synergistic effect on the growth of rice seedlings. The relationship between sclerin and some other plant growth regulators in the enzyme formation of germinating seeds was also described.     

Influence of exogenous sugars and polyols on C1-influx and efflux by the ascomycete Neocosmospora vasinfecta.

Glucose and other transportable sugars and polyols inhibited Cl- influx very soon after addition to mycelium in the process of Cl- accumulation. Under the usual experimental conditions (0.1 mM KCl, glucose greater than or equal to 2 mM) the mean percentage of inhibition of Cl- influx by glucose was 54.1 +/- 8.0 (+/- standard error; N = 26). Transport of the exogenous carbohydrate was necessary for inhibition of Cl- influx. Thus, the estimated Ki for glucose inhibition of Cl- influx (28 muM) was close to the Km for glucose transport; glycerol did not inhibit Cl- influx unless it was itself transported, and the degree of inhibition exerted by various carbohydrates correlated with their uptake rates. Inhibition was not caused by the accumulated sugar itself, as high levels (ca. 60 mM) of intramycelial 3-O-methylglucose gave rise to a stimulation of Cl- influx when the exogenous sugar was removed. It is suggested that interaction of Cl- and carbohydrate transport arises from competition for a common energy-coupling mechanism in the cell membrane. Both glucose and 3-O-methylglucose elicited Cl- efflux, but the maximal Cl- efflux rates were observed only after 40 min of incubation and only in the presence of the readily metabolizable glucose. Removal of the exogenous glucose, even after maximal Cl- efflux had been established, resulted in the rapid cessation of efflux. Studies under anaerobic conditions gave further evidence that glucose uptake was necessary and that efflux was not due to temporary depletion of energy reserves. It is proposed that glucose-induced leakage of Cl- is due to reversal of the Cl- uptake system, even though the Km for efflux is much greater than that for influx.     

Synthetic Racemate and Enantiomers of Cytosporone E,a Metabolite of an Endophytic Fungus,Show Indistinguishably Weak Antimicrobial Activity

The racemate and the enantiomers of cytosporone E [3-heptyl-4,5,6-trihydroxyphthalide (1)], a metabolite of the endophytic fungus, CR200 (Cytospora sp.), were synthesized. The key steps were (i) Sharpless asymmetric dihydroxylation of an alkene (8) and (ii) HPLC separation of the enantiomers of tert-butyldimethylsilyl ether (12) on a chiral stationary phase. The racemate and enantiomers of cytosporone E showed only weak antimicrobial activity with no difference among them.     

Structure and Biological Activity of Plant Growth Regulators Produced by Penicillium sp. No. 31f

A phenolic amide, N-p-coumaroyltyramine (1), was isolated as an α-glucosidase inhibitor from methanol extracts of Welsh onion (Allium fistulosum). The inhibitory activity of 1 against a yeast enzyme was as high as K_i 8.4 × 10^?7 m. From a structure-activity relationship study of 1 and its related compounds, the occurrence of α-glucosidase inhibitory activity required a p-coumaramide structure, with an amide hydrogen and alkyl or aralkyl substituent on the amide part.     

协同伴侣分子CHIP的E3连接酶活性及其生物学意义

CHIP(carboxy terminus of Hsc70 interacting protein)是一种新发现的具有泛素化连接酶活性的协同分子伴侣,它N端有TPR(the tetratricopeptide repeat)结构,可以和分子伴侣结合,C端有U-box结构,具有E3酶功能.CHIP可以介导一系列重要蛋白质的泛素化降解,从而维持细胞内蛋白质的质量.现就CHIP的结构和功能、CHIP的底物特征、CHIP的生物学作用以及CHIP在疾病发生中的可能作用做一综述.     

Biological Activity of a Phytotoxic Glycopeptide Produced by Corynebacterium sepedonicum

A purified toxic glycopeptide from Corynebacterium sepedonicum (Speick.) Dows., possesses the capacity to wilt plant cuttings. The toxin induces a rapid general flaccidity in stem tissues followed by a leaf wilt making its effects significantly different from that induced by high molecular weight substances (dextrans). In the latter case, the initial effect of a dextran induced wilt is a leaf wilt presumably caused by the plugging of xylem elements. However, physiological experiments including dye transport studies, plasmolytic studies, measurements on electrolytes, studies on the movement of ³H₂O through tomato cuttings, and toxin binding studies all strongly suggest that the primary effect of the toxin is to destroy the integrity of cellular membranes resulting in the net loss of water from the cell. Membrane damage in toxin treated plants was confirmed by electron microscopic observations. Evidence of damage were seen in chloroplasts, mitochondria, the plasma membrane, and the structural integrity of the cell wall. These effects appeared to be a direct cause and not a secondary result of the toxin as shown by autoradiographic studies using ³H-toxin.     

Isolation and Biological Activity of Cyl-2, a Metabolite of Cylindrocladium scoparium

Three metabolites designated Cyl–1, –2 and –3 were isolated as plant growth regulators from culture filtrate of Cylindrocladium scoparium Morgan, a phytopathogenic fungus. Cy1–2 was obtained as pure crystals, and it revealed marked inhibitory activity on the root growth of lettuce seedlings. Cyl–1 showed inhibition on the same organ, while Cyl–3 showed promotion.