丁香假单胞菌环式脂肽毒素的生理和分子生物学研究

综合评述了近10年来在丁香假单胞菌脂肽毒素生理和分子生物学研究上的发现。这些毒素依肽部AA数目可分两组。丁香假单胞霉素组(syringomycuns)已报告4个成员,肽部有9个AA;丁香假单胞肽毒素组有2个成员,肽部分别有22个和25个AA。肽部C端羧基与分子内羟基氨基酸残基(AA)的羟基酯化闭合成环,再由羟基脂肪酸酰化。两组毒素都诱导植物电解质渗漏、人和动物红血球溶解,其机制在于在细胞膜上形成二价阳离子可通过的寡体通道。对酵母菌的抑制作用受固醇的种类影响,以胆固醇的保护作用最强。丁香假单胞霉素的合成涉及一个多酶系统,有些负责肽合成,有些负责运输或调节,除受内源调节蛋白调节外,也受外源信号分子调节,尤其是受植物酚糖苷诱导。这些毒素具有抗真菌活性,对人和动物的一些病原霉菌有明显效果,在试验剂量无副作用,在医药上应用的前景良好。     

Paecilopeptin,a New Cathepsin S Inhibitor Produced by Paecilomyces carneus

Paecilopeptin, a novel cathepsin S inhibitor, was produced and isolated from the culture supernatant of the fungal strain, Paecilomyces carneus. A spectroscopic analysis revealed the planar structure of paecilopeptin to be acetyl-Leu-Val-CHO. The stereochemistry of the constituent amino acids was analysed by chiral HPLC after oxidation and 6N HCl hydrolysis of paecilopeptin. The total synthesis of paecilopeptin was completed in six steps. Paecilopeptin inhibited human cathepsin S with an IC₅₀ value of 2.1 nM in vitro.     

A Complement Inhibitor Produced by Stachybotrys complementi,nov. sp. K-76, a New Species of Fungi Imperfecti

A complement inhibitor, K-76, was isolated and purified from the culture supernatant of a fungus, Stachybotrys complementi, nov. sp. K-76, isolated from soil of Ishigaki Island, Okinawa. K-76 is a sesquiterpene compound and it can be oxidized to a monocarboxylic derivative (K-76 COOH), the sodium salt of which is very soluble and much less toxic than K-76. K-76 and K-76 COOH both inhibited complement activation by either the classical or alternative pathway. They inhibited generation of the factor chemotactic to human polymorphonuclear leukocytes from human serum by aggregated immunoglobulin. When sensitized erythrocytes were treated with complement in the presence of K-76 COOH, the resulting unlysed cells were found to be in the state of EAC1, 4b, 2a, 3b. Thus K-76 COOH is considered to block mainly the C5 intermediate step. K-76 COOH did not inhibit any proteases or esterases tested, except when tested at high concentration.     

Two New Pyrrolosesquiterpenes Produced by a Streptomyces Species

Two new pyrrolosesquiterpenes, 1 and 2 , were isolated from cultures of the soil actinomycete Streptomyces sp. Hd7–21. The structures of these compounds were established as (2Z,4E,9E)‐6,7,11‐trihydroxy‐3,7,11‐trimethyl‐1‐(1H‐pyrrol‐2‐yl)dodeca‐2,4,9‐trien‐1‐one ( 1 ) and (2Z,4E)‐5‐{3‐[(2E)‐4‐hydroxy‐4‐methylpent‐2‐en‐1‐yl]‐3‐methyloxiran‐2‐yl}‐3‐methyl‐1‐(1H‐pyrrol‐2‐yl)penta‐2,4‐dien‐1‐one ( 2 ) by extensive spectroscopic analyses including MS, and 1D‐ and 2D‐NMR data. Their cytotoxic activities against a panel of human cancer cell lines were evaluated.     

Agar-Like Polysaccharide Produced by a Pseudomonas Species: Production and Basic Properties

A new species of Pseudomonas was isolated that produced copious amounts of an exocellular heteropolysaccharide (PS-60) after incubation for 3 days at 30°C in media containing 3% glucose as a carbon source. The polysaccharide was composed of approximately 46% glucose and 30% rhamnose and, in addition, contained 21% uronic acid and 3% O-acetyl. Upon deacetylation by a mild alkaline treatment, PS-60 produced a brittle, firm, and optically clear gel. This gelling property was thermoreversible. The PS-60 gel exhibited excellent heat stability that withstood autoclaving (i.e., 121°C for 15 min) for several cycles. The gel strength, melting point, and setting point of the polysaccharide were controlled primarily by the concentration of cations. PS-60 was not affected by a variety of enzymes. The results of tests involving various culture media and biochemical test media indicate that PS-60 is an excellent alternative gelling agent to agar.     

Absorption and Fluorescence of Water-Soluble Pigments Produced by Four Species of Pseudomonas

Pigments produced by four species of Pseudomonas during growth in three media were examined for visible and ultraviolet absorption. Ultraviolet fluorescence excitation and emission spectra were obtained. In all pigments, an absorption maximum occurs at 405 mμ. Ultraviolet excitation of fluorescence occurs primarily at 400 to 410 mμ, with smaller maxima at 460 mμ, or 525 mμ, depending on pH, bacterial species, or medium. Emission maxima, after excitation at 410 mμ, occur at 390 mμ, and 455 to 475 mμ. The differences in fluorescence spectra may be used for taxonomic classification of the Pseudomonas.     

Adipose-derived exosomes deliver miR-23a/b to regulate tumor growth in hepatocellular cancer by targeting the VHL/HIF axis

Journal of Physiology and Biochemistry - Adipose tissue has long been considered to be involved in tumor progression. However, the adipocyte-secreted molecular determinants that regulate...     

Identification of the Biosynthetic Gene Cluster for 3-Methylarginine,a Toxin Produced by Pseudomonas syringae pv. syringae 22d/93

The epiphyte Pseudomonas syringae pv. syringae 22d/93 (Pss22d) produces the rare amino acid 3-methylarginine (MeArg), which is highly active against the closely related soybean pathogen Pseudomonas syringae pv. glycinea. Since these pathogens compete for the same habitat, Pss22d is a promising candidate for biocontrol of P. syringae pv. glycinea. The MeArg biosynthesis gene cluster codes for the S-adenosylmethionine (SAM)-dependent methyltransferase MrsA, the putative aminotransferase MrsB, and the amino acid exporter MrsC. Transfer of the whole gene cluster into Escherichia coli resulted in heterologous production of MeArg. The methyltransferase MrsA was overexpressed in E. coli as a His-tagged protein and functionally characterized (K_m, 7 mM; k_cat, 85 min⁻¹). The highly selective methyltransferase MrsA transfers the methyl group from SAM into 5-guanidino-2-oxo-pentanoic acid to yield 5-guanidino-3-methyl-2-oxo-pentanoic acid, which then only needs to be transaminated to result in the antibiotic MeArg.Microbial plant pathogens cause severe losses in agriculture each year (1). For example, the plant pathogen Pseudomonas syringae pv. glycinea is responsible for bacterial blight of soybean, a leaf spot disease of great economic impact. Besides chemical treatment, biocontrol agents that antagonize microbial plant pathogens are gaining increasing importance in fighting plant diseases (6, 11, 27). In a screening for possible biocontrol strains, an epiphytic bacterium showing a strong and selective activity against the pathogen P. syringae pv. glycinea was isolated from soybean leaves (29). The strain was characterized as Pseudomonas syringae pv. syringae 22d/93 (Pss22d). The antagonism of Pss22d against P. syringae pv. glycinea has been demonstrated successfully in vitro and in planta under greenhouse and field conditions (19, 29). In order to identify the molecular basis of the antagonism of Pss22d against P. syringae pv. glycinea, we focused on its secondary metabolites. Besides the well-known lipodepsipeptides syringomycin and syringopeptin (3), Pss22d produces the rare amino acid 3-methylarginine (MeArg) (5). As little as 20 nmol of MeArg strongly and selectively inhibits P. syringae pv. glycinea but no other pseudomonads in vitro (29). Since the inhibition can be compensated for by l-arginine supplementation but not by any other essential amino acid, it is likely that the toxin acts as an inhibitor of the arginine biosynthesis pathway or an arginine-dependent pathway, such as nitric oxide formation (13, 16). Feeding experiments and Tn5 transposon mutagenesis suggested that MeArg is produced by an S-adenosyl methionine (SAM)-dependent methyltransferase (5) converting the enol of 5-guanidino-2-oxo-pentanoic acid to 5-guanidino-3-methyl-2-oxo-pentanoic acid. An analogous reaction is known to occur with the methyltransferases GlmT, DptI, and LptI, which form 3-methylglutamate from α-ketoglutarate (18). On the way to MeArg, only a transaminase catalyzing the formation of MeArg from 5-guanidino-3-methyl-2-oxo-pentanoic acid and an amino acid exporter to secrete the toxin would be needed.Here, we describe the identification and functional characterization of the MeArg biosynthesis gene cluster from the epiphyte Pss22d.     

Enzymes Produced by a Pseudomonas Species Which Inactivate Inhibitors of Certain Viral Hemagglutinins. I. Identification and Purification of a Proteinase and Phospholipase C

Filtrates from cultures of a psychrophilic Pseudomonas species, which inactivate serum inhibitors of certain viral hemagglutinins, were shown to contain both lecithinase (phospholipase C) and a proteolytic enzyme with elastase activity. The bacterium was cultivated under conditions favoring production of the respective enzymes, and the enzymes were purified by ammonium sulfate precipitation followed by column chromatography or by gel filtration. The elastase was obtained in crystalline form and was recrystallized. It has properties similar to those of a number of other bacterial elastases but is more heat-labile than most. Although a high degree of purification was achieved for the lecithinase, as evidenced by an increase in specific activity, it was not obtained in crystalline form. Partially purified preparations of the lecithinase had extremely high activity compared to that of commercial preparations of phospholipase C from Clostridium welchii.     

Volatile Compounds Produced in Sterile Fish Muscle (Sebastes melanops) by Pseudomonas putrefaciens, Pseudomonas fluorescens, and an Achromobacter Species

Volatile compounds produced by Pseudomonas putrefaciens, P. fluorescens, and an Achromobacter species in sterile fish muscle (Sebastes melanops) were identified by combined gas-liquid chromatography and mass spectrometry. Compounds produced by P. putrefaciens included methyl mercaptan, dimethyl disulfide, dimethyl trisulfide, 3-methyl-1-butanol, and trimethylamine. With the exception of dimethyl trisulfide, the same compounds were produced by an Achromobacter species. Methyl mercaptan and dimethyl disulfide were the major sulfur-containing compounds produced by P. fluorescens.     

In Silico Analysis Identification of a Novel Germ-Line VHL Mutation in a Patient of Malignant Pheochromocytoma

Objective: Von Hippel-Lindau (VHL) disease is an autosomal dominantly inherited tumor syndrome caused by a VHL gene mutation. Here we report a novel mutation of VHL in a patient diagnosed with malignant pheochromocytoma at the age of 17.Methods: A 17-year-old female was referred for paroxysmal supraventricular tachycardia and anemia. She was diagnosed with a left adrenal pheochromocytoma based on biochemical and imaging studies. A left adrenalectomy was performed. Six months after surgery,

A Case of Calciphylaxis in a Patient with Hypoparathyroidism and Normal Renal Function

Blake L. Erdel, MD, Rattan Juneja, MD, Carmella Evans-Molina, MD, PhD

Osteomesopyknosis: A Case Report and Review of Sclerosing Bone Disorders

Ada Lyn M. Yao, MD, Pauline M. Camacho, MD, FACE

Diagnostic Challenge of Pheochromocytoma in a Patient Receiving Levodopa for Parkinson’s Disease

Masanori Shimodaira, MD, PhD; Tomohiro Niwa, MD; Koji Nakajima MD, PhD; Mutsuhiro Kobayashi, MD, PhD