The kinetics of the autolytic phase of growth in cultures of Aspergillus niger

The kinetics of the autolytic phase of growth in cultures of Aspergillus niger has been studied. Two different autolytic periods could be distinguished. One, consisting of a rapid (exponential) loss (62%) of mycelial weight, occurred between 36 and 117 hours of incubation. A second, consisting of a slow autolysis, occurred between the 117th and the 190th hour of incubation; the mycelial loss here being 5%. Based on the degree of autolysis (=67.0%), 92.5% and 7.5% are lost during the first and the second autolytic periods, respectively.     

Autolytic activities of the cell wall in rice coleoptiles. Effects of nojirimycin

Oryza sativa L. var. bahia coleoptile cell walls show sufficient autolytic activity for the release into the surrounding medium of amounts up to 60 μg of sugars per mg of dry weight of cell wall. The products released elute in Bio-gel P.2 as mono- and polysaccharides with glucose as the sole component. The polysaccharide component releases tri- and tetrasaccharides on treatment with a glucanase specific for β (1–3) (1–4) linkages in the same proportion as that of the mixed glucan of the cell wall. This supports the hypothesis that the polysaccharide component originates from the cell wall glucan and that autolysis is therefore related to the processes of the loss of rigidity of the cell wall. Nojirimycin (a specific glucanase inhibitor and inhibitor of auxin-induced elongation) decreases autolytic activity of the cell walls, reducing it to 30% of its normal value. Bio-gel P. 2 elution of the products released in autolysis in the presence of nojirimycin shows that only the monosaccharide fraction was affected.     

The dynamics of T-cell fratricide: application of a robust approach to mathematical modelling in immunology

Fratricide between CD8(+) T lymphocytes is known to occur in HTLV-I and possibly HSV-1 and HIV-1 infection. However it is not known what effect, if any, T-cell fratricide has on the course of infection. Here we present simple mathematical techniques to investigate T-cell fratricide with particular reference to HTLV-I infection. Using a general model we predict the qualitative and quantitative effect of fratricide on HTLV-I equilibrium proviral load. We also investigate the effect of fratricide on the probability of viral clearance. We show that, surprisingly, fratricide can lead either to an increase or a decrease in equilibrium proviral load. We derive the conditions necessary for fratricide to cause a decrease in load and deduce that, for the five HTLV-I-positive patients considered here, fratricide has probably caused an increase in equilibrium load. We also estimate the percentage increase in load that is attributable to fratricide and determine the parameters that should be measured in order to improve this estimate. Finally, we show that fratricide reduces the probability of viral clearance. Mathematical modelling of HTLV-I infection, as is often the case in biology, is severely hampered by a lack of experimental data. Consequently it is difficult to know what functional form a model should take. The behaviour of complex nonlinear systems is highly model-dependent. Predictions based on theoretical models are therefore sensitive to the choice of model; this is a very severe problem that undermines and limits the success of the application of mathematics to immunology. In this paper we reduce the model dependency of the results in two ways-by considering (analytically) a general model with a minimal number of assumptions and, where this is not possible, by checking (numerically) that a wide range of models yield the same results. We therefore begin to develop two practical methods for dealing with the problem of robustness in mathematical models of the immune system.     

Endochitinase from Aspergillus nidulans implicated in the autolysis of its cell wall

An endochitinase from centrifuged autolyzed cultures of Aspergillus nidulans has been purified 100 times. The enzyme has Mw 27,000, pI of 4.8 units, pH optimum around 5 pH units. It is unstable at temperature greater than 70 degrees C and does not have a cation requirement. It is inhibited by Hg2+, Cu2+, Ca2+ and Ag+ and it does not have muramidase activity. The enzyme depolymerizes chitin rapidly with production of high molecular weight polysaccharides, and then slowly degrades these with production of N,N'-diacetylchitobiose. The enzyme hydrolyzes N,N',N'-triacetylchitotriose with production of N,N'-diacetylchitobiose and N-acetylglucosamine and this hydrolysis is inhibited by other chitin oligomers and N-acetylglucosamine. This enzyme hydrolyzes in the same way the chitin obtained from the cell wall of Aspergillus nidulans.     

果实表达PGIPs的基因克隆及功能研究进展

多聚半乳糖醛酸酶(PGs)是病原真菌早期侵染植物的一个重要致病因子。多聚半乳糖醛酸酶抑制蛋白(PGIPs)作为植物防御蛋白,能特异性抑制真菌分泌的多聚半乳糖醛酸酶,并通过延长寡聚半乳糖醛酸(OGs)的稳定期激活植物防御反应。综述PGIPs在植物细胞中的定位,PGIPs与PGs之间的作用方式,PGIPs基因的分离与克隆,以及PGIPs对果实感病的影响,并对PGIPs的研究前景进行展望。     

Degradation of DNA during the autolysis of<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis>

The autolysis of yeast cells has practical implications in the production of fermented foods and beverages and flavourants for food processing. Protein and RNA degradation during yeast autolysis are well described but the fate of DNA is unclear. Yeast cells (Saccharomyces cerevisiae) were autolysed by incubating suspensions at 30–60°C (pH 7.0), and at pH 4.0–7.0 (40°C) for 10–14 days. Up to 55% of total DNA was degraded, with consequent leakage into the extracellular environment of mainly 3′- and 5′-deoxyribonucleotides, and lesser amounts of polynucleotides. The rate and extent of DNA degradation, composition of the DNA degradation products and DNase activity were affected by temperature and pH. The highest amount of DNA degradation occurred at 40°C and pH 7.0, where the highest DNase activity was recorded. DNase activity was lowest at 60°C and pH 4.0, where the proportion of polynucleotides in the degradation products was higher. Electronic Publication     

环境因素对酸奶菌株自溶的影响

本论文探究了培养条件对德氏乳杆菌保加利亚亚种KLDS 1.9201和唾液链球菌嗜热亚种KLDS 3.021自溶的影响.结果表明,随着培养温度(30℃～55℃)、盐浓度(0%～5%)以及酸度值(pH5.0～7.5)的升高,KLDS 1.9201和KLDS 3.0201不仅自溶度相应增大,而且在磷酸缓冲液中释放的核酸和蛋白含量也呈递增趋势.高温55℃,pH 7.5和5%乳酸盐浓度的培养环境使KLDS 1.9201和KLDS 3.0201在培养45 h后的自溶度分别达到了55%和36.3%,显著高于低自溶培养环境下(30℃、pH 5.5和0%乳酸盐)KLDS 1.9201和KLDS 3.0201的自溶度9.96%和8.6%(P<0.05).透射电镜观察表明高自溶和低自溶培养条件对酸奶菌株菌体形态的影响是截然不同的,且酸奶菌株自溶时发生的细胞壁降解程度与自溶光密度值相对应.     

Development of tricyclic hydroxy-1H-pyrrolopyridine-trione containing HIV-1 integrase inhibitors

New tricyclic HIV-1 integrase (IN) inhibitors were prepared that combined structural features of bicyclic pyrimidinones with recently disclosed 4,5-dihydroxy-1H-isoindole-1,3(2H)-diones. This combination resulted in the introduction of a nitrogen into the aryl ring and the addition of a fused third ring to our previously described inhibitors. The resulting analogues showed low micromolar inhibitory potency in in vitro HIV-1 integrase assays, with good selectivity for strand transfer relative to 3′-processing.     

抑制黑色素合成的乳酸菌胞外多糖的筛选和性质研究

【目的】筛选可抑制黑色素合成的乳酸菌胞外多糖。【方法】通过观察凝乳拉丝外观筛选产胞外多糖的乳酸菌菌株,测量胞外多糖对B16黑色素瘤细胞黑色素合成和细胞活力的影响。对胞外多糖进行纯化,并通过PMP衍生-HPLC、红外光谱、抑制酪氨酸酶活性、抗氧化能力对其单糖组成和结构、作用机制进行研究。【结果】筛选到一株乳酸菌Lactobacillus rhamnosus HLAB122,发酵产生的胞外多糖在5 g/L浓度下可使B16细胞黑色素产量下降至空白对照的32.7%,且在96 h内对细胞活力无影响。纯化后的多糖由鼠李糖、葡萄糖、半乳糖构成,各单糖摩尔比为1?5.44?5.37。该胞外多糖不抑制酪氨酸酶活力且抗氧化性微弱。【结论】L.rhamnosus HLAB122产生的胞外多糖在个人护理产品中有潜在应用价值。     

酵母菌细胞自溶突变株的研究

细胞壁是酵母菌的重要细胞器 ,参与细胞内外多方面的生理生化过程 ,如细胞絮凝、信号转导、致病性等 ,在决定细胞结构完整性方面起着重要的作用。酵母细胞壁是由 β - 1 ,3-葡聚糖、β - 1 ,6-葡聚糖、甘露聚糖蛋白及几丁质等相互交链构成的复杂的双层网状结构[1] 。细胞壁组成或结构的改变会使细胞产生对温度或低渗透压的敏感性 ,在相应的条件下发生自溶 ,使细胞内容物释放到胞外。产生上述效应的突变株称为温度敏感自溶突变株和低渗透敏感自溶突变株[2～ 4 ] 。对此类突变株的研究一方面有利于进一步阐明酵母菌细胞壁代谢及组装的调控机制…     

β-N-Acetylglucosaminidase from Aspergillus nidulans which degrades chitin oligomers during autolysis

A hexosaminidase from autolyzed cultures of Aspergillus nidulans was purified 196 fold and characterized as a beta-N-acetylglucosaminidase (EC 3.2.1.30). The enzyme has a MW of 190000, a pI of 4.3, and optimum pH of 5.0 and is unstable at temperatures above 50 degrees C. The enzyme is a glycoprotein with 19.5% sugars, mannose being the principal component. It binds strongly to chitin. The enzyme hydrolyzes different substrates. The Ki with the competitive inhibitor 2-acetamido-2-deoxy-D-gluconolactone was independent of the substrate used. The enzyme was inhibited by Hg2+, Ag+, acetate and other organic anions. The kinetics of hydrolysis of chitin oligosaccharides from 2 to 6 units was studied by HPLC. This enzyme is an exoenzyme which degraded chitin oligomers gradually with the production of N-acetylglucosamine. The hydrolysis of N-N'-diacetylchitobiose was inhibited non-competitively by glucosamine and N-acetylglucosamine. In mixtures of chitin oligosaccharides, the hydrolysis of chitobiose was competitively inhibited by each of the other oligomers.     

Evaluation of lactic acid bacteria autolysate for the supplementation of lactic acid bacteria fermentation

At the end of culture in a carbon-limited medium, i.e. the best conditions for subsequent autolysis, lactic acid bacteria were harvested and autolysed at 50 °C for 24 h. The resulting supernatant was then successfully tested as a substitute for industrial yeast extract for the supplementation of whey permeate and its conversion into lactic acid: for almost equivalent total nitrogen amounts of both supplements, the same growth and production rates were recorded.     

Purification and properties of a 1,3-β-glucanase from Penicillium oxalicum autolysates

High 1,3-beta-glucanase activity was detected during autolysis in a culture medium containing Penicillium oxalicum. It was due to the combined action of four enzymes. The purification process for the major enzyme produced a homogeneous band in the SDS polyacrylamide gel that corresponded to a molecular weight of 79,400 daltons. The enzyme pI was 6.3 and it was only active against 1,3-beta-glucans, with a S0.5 of 0.23 mg ml-1 against laminarin. The enzymatic optima were found at pH 4 and 55 degrees C, and instability was evident when pH and temperature were altered. The enzyme was not active against oxidated laminarin and was barely inhibited by glucono-D-lactone. Hg2+, Ag+ and Fe2+ were effective inhibitors. The enzyme was adsorbed by concanavalin-A-sepharose.     

Partial purification and characterization of cysteine proteinase inhibitor from chicken plasma

A high-molecular-weight cysteine proteinase inhibitor (CPI) was purified from chicken (Gallus gallus) plasma using polyethylene glycol (PEG) fractionation and affinity chromatography on carboxymethyl–papain–Sepharose-4B. The CPI was purified 96.8-fold with a yield of 28.9%. Based on inhibitory activity staining for papain, CPI was shown to have an apparent molecular mass of 122 kDa. No inhibitory activity was obtained under reducing condition, indicating that CPI from chicken plasma was stabilized by disulfide bonds. CPI was stable in temperature ranges from 40 to 70 °C for 10 min; however, more than 50% of the inhibitory activity towards papain was lost within 30 min of heating at 90 °C. CPI was stable in the presence of salt up to 3%. The purified CPI exhibited the inhibitory activity toward autolysis of arrowtooth flounder (Atheresthes stomias) and Pacific whiting (Merluccius productus) natural actomyosin (NAM) in a concentration-dependent manner.     

β-Glucosidase from the cellulolytic system of Alternaria alternata autolyzed cultures

Abstract A β-glucosidase from centrifugated autolyzed cultures of Alternaria alternata has been purified 71 times by Sephadex G-200, CM-Biogel A and DEAE-Biogel A successively. The enzyme is a glycoprotein with 16% sugar and a M _r of 160 000, formed by two subunits of 60 000 and 80 000. The enzyme has optimum pH of 5 units and optimum reaction temperature of 50°C, being stable in a pH range of 3–8 and 0 to 60°C. The enzyme hydrolyzes different substrates showing maximum affinity and maximum hydrolysis velocity on cellobiose. The β-glucosidase is inhibited by gluconolactone but not by 10 mM glucose.     

Protoplast production from filamentous fungi with their own autolytic enzymes

Abstract Production of protoplasts in different genera of filamentous fungi with their own lytic enzymes obtained from autolyzed cultures, as well as the regeneration of these protoplasts, has been studied. The results support the idea that the use of these autolytic enzymes could be a general method of production of protoplasts from filamentous fungi.     

Ritonavir does not inhibit calpain in vitro

Ritonavir, an inhibitor of HIV-1 protease, has been reported to also inhibit the Ca2+-dependent cysteine protease, calpain. We have investigated these claims with an in vitro study of the effect of ritonavir on the m-calpain and mu-calpain isoforms. Ritonavir failed to block either autolytic or hydrolytic calpain activity, but remained fully capable of inhibiting the HIV-1 protease. Any calpain-related effects of ritonavir in cells must, therefore, arise by a mechanism other than direct inhibition of calpains.     

Acrylonitrile induces autolysis Bacillus subtilis

Acrylonitrile (AN) is an industrial chemical used in the manufacture of plastics and other polymers. AN has been reported to be an acute toxin and is a known carcinogen in rodents. When AN was mixed with suspensions of Bacillus subtilis, the bacteria began autolysis. It was determined that AN is partially converted to cyanide, a strong protonophore in B. subtilis. Autolytic enzymes in B. subtilis become active when the protonmotive force is dissipated. The amount of cyanide produced from AN, however, was not enough to promote autolysis in exponential B. subtilis. This is the first report showing that AN may induce autolytic reactions in bacteria. It is suggested the autolysis of B. subtilis may be useful in the environmental monitoring of AN. In addition, the metabolism of AN by bacilli may be useful in bioremediation.     

Purification and properties of a β-glucosidase from Penicillium oxalicum autolysates

A beta-glucosidase from the medium of an autolyzed culture of Penicillium oxalicum has been purified by tannic acid precipitation, sephacryl S-200, DEAE-Biogel, CM-Biogel and Mono Q successively. The purification process produced a homogeneous band in the SDS-PAGE that correspond to a Mr of 133,500. The enzyme had a pl of 4, and the active optima were found at pH 5.5 and 55 degrees C. The enzyme hydrolyzed different substrates showing maximum affinity against p-nitrophenyl-beta-D-glucoside with a Km value of 0.37 mM. The beta-glucosidase was inhibited by Glucono-D-lactone but not by glucose in the concentration range of 1 to 10 mM. The enzyme was adsorbed by Concanavalin-A-Sepharose.