Synthesis of an Isoglutathione Derivative by Proteases and Its α→γ Transpeptidation

Benzyloxycarbonyl-l-cysteine and glycine benzhydrylamide were condensed by papain in a yield of 39.5%. After elimination of the N-protecting group, l-cysteinylglycine benzhydrylamide was condensed with benzyloxycarbonyl-l-glutamic acid by acid protease from Irpex lacteus Fr. in a yield of 21.0%. From the isoglutathione derivative thus obtained, a γ-linkage between glutamic acid and cysteine was formed by α → γ transpeptidation in alkaline conditions after esterification of γ-carboxylic acid.     

Biochemical Studies on Ricin Part X Effect of the Two Constituent Polypeptide Chains of Ricin D toward Mouse Sarcoma Ascite Tumor Cells

A maltotetraose-forming amylase from Pseudomonas stutzeri was highly purified by adsorption on starch granules and by chromatographies on Sephadex G-100 and DEAE-cellulose. The purified enzyme showed a single band in polyacrylamide gel electrophoreses with or without sodium dodecylsulfate. The optimum pH for enzyme action on starch was 6.0-6.5, and the optimum temperature was 45°C. The purified enzyme attacked starch from the non-reducing end to produce α-anomer oligosaccharides. This indicated that the enzyme was an exo-α-amylase which had not hitherto been found. The enzyme activity was markedly inhibited by the addition of Cu²⁺, Hg²⁺, N-bromosuccinimide and 2,3-butanedione. The molecular weight of the enzyme determined by the method of Weber and Osborn was about 5.7 × 10⁴. The isoelectric point of the enzyme was estimated to be 5.3 by polyacrylamide gel electrofocusing. The Km and k₀ values of this enzyme for starch, glycogen, short chain amylose and some maltooligosaccharides were calculated from Lineweaver-Burk plots.     

Characterization of chitinase from Streptomyces luridiscabiei U05 and its antagonist potential against fungal plant pathogens

Streptomyces luridiscabiei U05 was isolated from wheat rhizosphere. It produced chitinase, which showed in vitro antifungal properties. The crude enzyme inhibited the growth of Alternaria alternata, Fusarium oxysporum, F. solani, Botrytis cinerea, F. culmorum and Penicillium verrucosum. The chitinase enzyme of the molecular weight of 45 kDa was purified using affinity chromatography of chitin. Streptomyces luridiscabiei U05 produced different chitinolytic enzymes. The highest enzyme activity was observed with the use of 4‐MU‐(GlcNAc)_, which points to the presence of an β‐N‐acetylhexosaminidase. The optimum activity was obtained at 35–40°C and pH 7–8. The enzyme showed thermostability at 35–40°C during 240 min of preincubation and lost its activity at 50°C and 60°C in 60 min. The chitinase activity from S. luridiscabei U05 was strongly inhibited by Hg²⁺ and Pb²⁺ ions, and sodium dodecyl sulphate (SDS). The Ca²⁺, Cu²⁺ and Mg²⁺ ions stimulated the activity of the enzyme.     

Volatile Composition and Biological Activities of the Leaf Essential Oil from Zanthoxylum limoncello Grown in Oaxaca,México

Zanthoxylum limoncello is a native plant from southern Mexico which is used as a timber source, condiment and as a traditional medicine. Herein, we report on the volatile content of the leaf essential oil and its biological activities. The annual essential oils (2015–2018) contained volatile organic compounds which exhibited a moderate growth inhibitory activity against H. pylori ATCC 53504 (MIC 121.4–139.7 μg mL^?1), 26695 (MIC 85.5–94.9 μg mL^?1) and J99 (MIC 94.7–110.4 μg mL^?1). These hydrodistillates contained 2‐undecanone (31.6–36.8 %; MIC 185.3–199.2 μg mL^?1) and 2‐undecenal (25.1–35.7 %; MIC 144.8–111.3 μg mL^?1) as the most abundant compounds which were partially involved in the anti‐H. pylori activity. The human ornithine decarboxylase enzyme (ODC1), which shows increased activity in several cancer types, was non‐competitively inhibited (V_max 2.7>0.8 K_cat s^?1) by the essential oil of Z. limoncello as well as by 2‐undecanone and 2‐undecenal in accordance to in vitro kinetic studies. In silico calculations strongly suggest that the carbonyl group of these oxygenated hydrocarbons interacts with both Asn319 and Ala39 at the subunit A of ODC1. Considering that Ala39 is located close to Asn44, a crucial amino acid of the ODC's allosteric site, the non‐competitive inhibition of the enzyme by 2‐undecanone and 2‐undecenal is endorsed. Finally, the essential oil of Z. limoncello and its main volatiles showed a significant (p<0.01) and prolonged repellent effect against Aedes aegypti.     

Purification and Some Properties of Extracellular Protease of Euglena gracilis Z

The extracellular protease of Euglena gracilis z was purified to a single protein. It was an endopeptidase as found by the Nunokawa’s method, and showed optimum pH for the proteinase, esterase and amidase activities at 7.3, 7.0 and 6.3, respectively. It had a molecular weight of 41,000 and isoelectric point of 8.3. The bleached mutant of E. gracilis produced higher activity of extracellular protease than the wild strain, and supplementation of peptone to the growth medium augmented the enzyme production in both green and bleached cells. The Euglena extracellular protease was markedly inhibited by diisopropylfluorophosphate and Streptomyces subtilicin inhibitor, and to lesser extents by EDTA and p-chloromercuribenzoate. The enzyme was potentiated by some sulfhydryl compounds, activated greatly by Fe²⁺ and stabilized by Ca²⁺ and K⁺.     

Tunicamycin Inhibits Biosynthesis of Acid Mucopolysaccharides in Cultures of Chick Embryo Fibroblasts

Enterobacter cloacae KY 3074 grown in a medium containing xanthine, hypoxanthine, guanine, or their nucleosides and nucleotides produced xanthine oxidase. The purified enzyme preparation showed a major protein band and a few minor bands in acrylamide gel electrophoresis. Molecular oxygen was the most effective electron acceptor. Ferricyanide and 2,6-dichlorophenolindophenol also served as electron acceptors, but NAD and NADP did not. Xanthine and hypoxanthine were good substrates, and guanine was also an effective substrate. The activity was inhibited by Ag²⁺, Cu²⁺, PCMB, and ascorbate. The spectrum of the Enterobacter enzyme resembled that of some known xanthine oxidizing enzymes, and this suggests a similarity in the prosthetic groups of these enzymes. The molecular weight of the native enzyme and subunit was 128,000 and 69,000, respectively.     

Ribulose-1,5-bis-phosphate carboxylase activity in altitudinal populations of Espeletia schultzii Wedd

The ribulose-1,5-bis-phosphate (RBPC) ¹⁴CO₂ fixation rate was measured at four different temperatures, 5°, 15°, 25° and 35° C, in three populations of Espeletia schultzii at different altitudes, 3100, 3550 and 4200 ma.s.l. The fixation rate increased with temperature increase in the populations studied. The population at 4200 m showed the higher rate at any temperature, followed by those at 3550 and 3100 m. The Km(CO₂) increased with temperature increase, but the values were similar among populations. The V _max values increased with temperature and were higher for the 4200-m population. These results suggest that the RBPC enzyme is more activated in the highland population and that the enzyme kinetics are not similar among populations.     

Purification and characterization of a trypsin-like enzyme with fibrinolytic activity present in the abdomen of horn fly, Haematobia irritans irritans (Diptera: Muscidae)

This work describes the purification and characterization of a trypsin-like enzyme with fibrinolytic activity present in the abdomen of Haematobia irritans irritans (Diptera: Muscidae). The enzyme was purified using a one-step process, consisting of affinity chromatography on SBTI-Sepharose. The purified protease showed one major active proteinase band on reverse zymography with 0.15% gelatin, corresponding to a molecular mass of 25.5 kDa, with maximum activity at pH 9.0. The purified trypsin-like enzyme preferentially hydrolyzed synthetic substrates with arginine residue at the P1 position. The K _m values determined for three different substrates were 1.88 × 10^–4, 1.28 × 10^–4, and 1.40 × 10^–4 M for H--benzoyl-Ile-Glu-Gly-Arg-p-nitroanilide (S2222), dl-Ile-Pro-Arg-p-nitroanilide (S2288), and DL-Phe-Pip-Arg-p-nitroanilide (S2238), respectively. The enzyme was strongly inhibited by typical serine proteinase inhibitors such as SBTI (soybean trypsin inhibitor, K _i = 0.19 nM) and BuXI (Bauhinia ungulata factor Xa inhibitor, K _i = 0.48 nM), and less inhibited by LDTI (leech-derived tryptase inhibitor, K _i = 1.5 nM) and its variants LDTI 2T and 5T (0.8 and 1.5 nM, respectively). The most effective inhibitor for this protease was r-aprotinin (r-BPTI) with a K _i value of 39 pM. Synthetic serine protease inhibitors presented only weak inhibition, e.g., benzamidine with K _i = 3.0 × 10^–4 M and phenylmethylsulfonyl fluoride (PMSF) showed traces of inhibition. The purified trypsin-like enzyme also digested natural substrates such as fibrinogen and fibrin net. The protease showed higher activity against fibrinogen and fibrin than did bovine trypsin. These data suggest that the proteolytic enzyme of H. irritans irritans is more specific to proteins from blood than are the vertebrate digestive enzymes. This enzyme's characteristics may be an adaptation resulting from the feeding behavior of this hematophagous insect.     

Participation of Mevalonate in the Biosynthetic Pathway of Ipomeamarone

1. The incorporation of mevalonate-2-¹⁴C into ipomeamarone in sweet potato root tissue infected by Ceratocystis fimbriata was demonstrated, but the rate was low when compared with acetate-2-¹⁴C. No dilution effect of mevalonate was noted during the incorporation of acetate-2-¹⁴C into ipomeamarone. This is very likely to result from the passive transfer of mevalonate into the cells.

2. No dilution effect of acetate during the incorporation of mevalonate-2-¹⁴C into ipomeamarone was noted. This indicates that mevalonate is not incorporated into ipomeamarone after its conversion to acetate.

3. Evidence for incorporation of acetate-2-¹⁴C into mevalonate was shown by the fact that the specific radioactivity of mevalonic acid benzhydrylamide was not lowered throughout repetitive crystallizations. These data also support the participation of mevalonate in ipomeamarone synthesis as an intermediate.

     

钙素对彩叶玉簪光合作用和保护酶活性的影响

该文以彩叶玉簪为材料,研究了不同钙素水平对玉簪叶片光合作用和保护酶活性的影响。结果表明:随着钙素水平的提高,彩叶玉簪叶片的净光合速率(Pn)、气孔导度(Gs)、胞间CO_2浓度(Ci)、蒸腾速率(Tr)和最大光化学效率(F_v/F_m)均呈单峰曲线,最高峰值出现在Ca~(2+)90 mg·L~(-1)时;电子传递速率(ETR)的变化也呈单峰曲线,峰值出现在Ca~(2+)50 mg·L~(-1)时;初始荧光(F_0)和最大荧光(F_m)值在0~360 mg·L~(-1)钙素水平下呈先升高后下降再升高的趋势,最大值均出现在90 mg·L~(-1)时;Pn和Gs值的变化与Ci值成正相关。同时叶片中过氧化物酶(POD)、过氧化氢酶(CAT)的活性及丙二醛(MDA)、可溶性蛋白质(SP)含量均表现为单谷曲线,在Ca~(2+)90 mg·L~(-1)时达最小值。超氧化物歧化酶(SOD)活性呈现持续下降趋势。综上所述,彩叶玉簪Pn下降主要由气孔引起,叶面喷施90 mg·L~(-1)的Ca~(2+)可增强彩叶玉簪光合作用,降低保护酶活性。     

Cloning and biochemical characterization of Staphylococcus aureus type IA DNA topoisomerase comprised of distinct five domains

DNA topoisomerases play critical roles in regulating DNA topology and are essential enzymes for cell survival. In this study, a gene encoding type IA DNA topoisomerase was cloned from Staphylococcus aureus (S. aureus) sp. strain C-66, and the biochemical properties of recombinant enzyme was characterized. The nucleotide sequence analysis showed that the cloned gene contained an open reading frame (2070 bp) that could encode a polypeptide of 689 amino acids. The cloned gene actually produced 79.1 kDa functional enzyme (named Sau-TopoI) in Escherichia coli (E. coli). Sau-TopoI enzyme purified from E. coli showed ATP-independent and Mg²⁺-dependent manners for relaxing negatively supercoiled DNA. The relaxation activity of Sau-TopoI was inhibited by camptothecin, but not by nalidixic acid and etoposide. Cleavage site mapping showed that the enzyme could preferentially bind to and cleave the sequence GGNN↓CAT (N and ↓ represent any nucleotide and cleavage site, respectively). All these results suggest that the purified enzyme is type IA DNA topoisomerase. In addition, domain mapping analysis showed that the enzyme was composed of conserved four domains (I through IV), together with a variable C-terminal region containing a unique domain V.     

The Production and Stability of Intracellular Myrosinase from Aspergillus niger

After Screening 100 micro-organisms to detect intracellular myrosinase, only Aspergillus niger produced myrosinase.

Enzyme production was induced by the addition of ten percent of a mustard extract^* to the culture medium. The enzyme was produced in considerable amounts on the first and second day of cultivation. L-Ascorbic acid was an excellent carbon source.

The enzyme was unstable but was stabilized by coexistence with 2-mercaptoethanol (10^?2 M) and ascorbic acid (10^?3 M).     

Purification and characterization of a thermostable uricase from Microbacterium sp. strain ZZJ4-1

In order to study the properties of a thermostable uricase produced by Microbacterium sp. strain ZZJ4-1, the enzyme was purified by ammonium sulfate precipitation and DEAE-cellulose ion exchange, hydrophobic and molecular sieve chromatography. The molecular mass of the purified enzyme was estimated to be 34 kDa by SDS-PAGE. The enzyme was stable between pH 7.0 and 10.00. The optimal reaction temperature of the enzyme was 30 °C at pH 8.5. The K _m and K _cat of the enzyme were 0.31 mM and 3.01 s⁻¹, respectively. Fe³⁺ could enhance the enzyme activity, whereas Ag⁺, Hg²⁺, o-phenanthroline and SDS inhibited the activity of the enzyme considerably. After purification, the enzyme was purified 19.7-fold with 31% yield. As compared with uricases from other microbial sources, the purified enzyme showed excellent thermostability and other unique characteristics. The results of this work showed that strains of Microbacterium could be candidates for the production of a thermostable uricase, which has the potential clinical application in measurement of uric acid.     

产壳聚糖酶内生真菌的筛选、鉴定及酶活力初步研究

植物内生真菌是挖掘不同类型壳聚糖酶及发现新酶的资源宝库。该研究从122株柑橘和血散薯内生真菌中筛选能产生壳聚糖酶的菌株,对其进行鉴定/初步研究酶活力影响因素,为后期其酶学性质及产壳聚糖酶内生真菌与宿主植物病害防御互作关系的研究奠定基础。通过透明圈法初筛结合液体发酵法进行复筛,得到2株可产生壳聚糖酶的内生真菌Stdif9和Stdif9-4,并发现Stdif9-4最高酶活力(0.968 U·mL^-1)显著高于Stdif9(0.780 U·mL^-1)。采用形态学和分子生物学结合的方法将菌株Stdif9-4鉴定为青霉属菌株,即Penicillium sp.Stdif9-4。通过DNS试剂法初步研究影响该菌株产壳聚糖酶活力的因素,发现不同培养时间对菌株壳聚糖酶活力具有显著影响,在培养96 h时,壳聚糖酶活力达到最大值。9种金属离子对菌株的酶活力具有不同影响,其中Mn²⁺和Ca²⁺对壳聚糖酶活力具有明显的激活作用;Ag⁺、Zn²⁺、Cd²⁺、Ba...     

Purification of a flavoprotein having NADPH-cytochrome c reductase and transhydrogenase activities from Nitrobacter winogradskyi and its molecular and enzymatic properties

A flavoenzyme which showed NADPH-cytochrome c reductase (NADPH-cytochrome c oxidoreductase EC 1.6.2.4) and transhydrogenase (NADPH-NAD⁺ oxidoreductase, EC 1.6.1.1) activities was purified to an electrophoretically homogeneous state from Nitrobacter winogradskyi. The reductase was a flavoprotein which contained one FAD per molecule but no FMN. The oxidized form of the enzyme showed absorption maxima at 272, 375 and 459 nm with a shoulder at 490 nm, its molecular weight was estimated to be 36,000 by SDS polyacrylamide gel electrophoresis, and the enzyme seemed to exist as a dimer in aqueous solution. The enzyme catalyzed reduction of cytochrome c, DCIP and benzylviologen by NADPH, oxidation of NADPH with menadione and duroquinone, and showed transhydrogenase activity. NADH was less effective than NADPH as the electron donor in the reactions catalyzed by the enzyme. The NADPH-reduction catalyzed by the enzyme of N. winogradskyi cytochrome c-550 and horse cytochrome c was stimulated by spinach ferredoxin. The enzyme reduced NADP⁺ with reduced spinach ferredoxin and benzylviologen radical.Abbreviations DCIP dichlorophenolindophenol - Tris trishydroxy-methylaminomethane - Mops 3-(N-morpholino) propanesulfonic acid - SDS sodium dodecylsufate     

Purification and characterisation of a novel alkalophilic α-D-mannosidase from Pseudomonas fluorescens

An extracellular alkaline α-D-mannosidase in the cell culture of a marine bacterium Pseudomonas fluorescens JK-02 was purified to homogeneity with a 30.7-fold by ammonium sulphate fractionation, anion-exchange chromatography and gel-filtration chromatography. The molecular weight of the purified enzyme was estimated to be 50.5 kDa based on the sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimal pH and temperature of the purified enzyme were 8.5 and 30°C. The K_m and V_max values of the purified enzyme towards p-nitrophenyl-α-D-mannopyranoside were determined to be 77 µM and 0.23 µM min^?1mg^?1 of protein, respectively. The α-D-mannosidase showed higher substrate specificity to α-1,3-mannobiose than other isomeric substrates such as α-1,2- and α-1,6-mannobiose. In addition, molecular characterisation of this enzyme reveals that it belongs to a class II α-mannosidase from the glycosyl hydrolase family 38. To the best of our knowledge, this is the first report on the alkalophilic α-1,3 D-mannosidase of Pseudomonas species, which has selective algal-lytic activity against Alexandrium tamarense, Akashiwo sanguine, Gymnodinium catenatum, Gymnodinium mikimotoi and Prorocentrum dentatum.     

硫肥对春油菜幼苗生理指标和土壤酶活性的影响

该研究以春油菜幼苗为材料,采用土壤盆栽试验,设7个不同施硫(0、35、70、105、140、175、210mg·kg^-1)处理,通过测定春油菜幼苗的株高、植株鲜重、叶绿素含量、MDA含量、SOD、POD、CAT活性、土壤全氮含量、pH、蔗糖酶、过氧化氢酶和脲酶活性指标,分析不同施硫量对春油菜幼苗生理生化指标和土壤相关酶活性的影响。结果表明:在春油菜苗期施用硫肥对幼苗的农艺性状、生理生化指标和土壤酶活性均产生了一定影响。施硫量在35~105mg·kg^-1范围时,对植株鲜重有明显的促进作用;施硫量在70~105mg·kg^-1范围时,类胡萝卜素含量达到最高;施硫量在70~105mg·kg^-1范围时,叶片中POD和CAT的活性明显升高,而MDA含量明显下降;经相关分析,MDA含量与POD活性呈极显著负相关(r=-0.92,P<0.01),与CAT活性呈显著负相关(r=-0.72,P<0.05),说明叶片MDA含量受POD和CAT活性变化的影响;施硫量高于105mg·kg^-1时,土壤脲酶和蔗糖酶活性受到抑制;施硫量高于140mg·kg^-1时,土壤过氧化氢酶活性受到抑制;随着施硫量的增加,土壤pH值和叶片SOD活性逐渐下降;经相关性分析,土壤脲酶活性和全氮含量间呈极显著正相关(r=1,P<0.01),表明土壤全氮含量受土壤脲酶活性变化的影响。由此可知,在低硫(35~105mg·kg^-1)条件下对春油菜幼苗生理生化指标及土壤酶活性具有一定的促进作用,而在高硫(>105mg·kg^-1)条件下则产生抑制。     

Properties of trehalase from different organs of alfalfa, <Emphasis Type="Italic">Medicago sativa</Emphasis>

Trehalase activity (THA) was identified in the cell-free extracts of various organs of Medicago sativa: roots, roots nodules, stems and leaves, as well as in seedlings and seeds. It showed the high activity at acid pH and optimal temperature ranged from 45° to 55°C. It was also differently affected by ions, i.e. the presence of calcium stimulated this activity but it was inhibited by Zn²⁺ and NH ₄ ⁺ . After separation by DEAE-cellulose chromatography and purification procedures, trehalase from alfalfa was purified 800 times, and Superose 12 HR gel filtration allowed to determine the molecular weight of 120 kDa for the native enzyme from the stems of alfalfa.     

A novel fibrinolytic enzyme from <Emphasis Type="Italic">Cordyceps militaris</Emphasis>, a Chinese traditional medicinal mushroom

A novel fibrinolytic enzyme from Cordyceps militaris was purified and partially characterized for the first time, which was designated C. militaris fibrinolytic enzyme (CMase). This extracellular enzyme from C. militaris was isolated by ammonium sulphate fraction, and purified to electrophoretic homogeneity using gel filtration chromatography. The apparent molecular mass of the purified enzyme was estimated to be 27.3 kDa by SDS-PAGE. The optimum pH and temperature for the enzyme activity were pH 6.0 and 25 °C, respectively. In the presence of metal ions such as Mg²⁺ and Fe²⁺ ions the activity of the enzyme increased, whereas EDTA and Cu²⁺ ion inhibited the enzyme activity. Interestingly the N-terminal amino acid sequences of the enzyme is extremely similar to those of the trypsin proteinases from insects, and has no significant homology with those of the fibrinolytic enzyme from other medicinal mushroom. In conclusion, C. militaris produces a strong fibrinolytic enzyme CMase and may be considered as a new source for thrombolytic agents.     

Characterization of <Emphasis Type="Italic">Mucor miehei</Emphasis> lipase immobilized on polysiloxane-polyvinyl alcohol magnetic particles

Mucor miehei lipase was immobilized on magnetic polysiloxane-polyvinyl alcohol particles by covalent binding. The resulting immobilized biocatalyst was recycled by seven assays, with a retained activity around 10% of its initial activity. K_m and V_max were respectively 228.3 M and 36.1 U mg of protein^–1 for immobilized enzyme. Whereas the optimum temperature remained the same for both soluble and immobilized lipase (45 °C), there was a shift in pH profiles after immobilization. Optimum pH for the immobilized lipase was 8.0. Immobilized enzyme showed to be more resistant than soluble lipase when assays were performed out of the optimum temperature or pH.