Conversion of potato phosphorylase isozymes

The conversion of a slow moving potato phosphorylase isozyme to a fast one, in sprouting tubers, either on freezing the whole tubers or on storage of their crude extracts, is due to limited proteolysis. High protease inhibitor concentration seems to be the primary factor preventing this conversion in freshly harvested tubers under similar conditions. Though MW determinations on both isozymes show the removal of a peptide during conversion, it is also likely that the enzyme may take up a different conformation due to the removal of this peptide.     

Purification and properties of α-1,4-glucan phosphorylase from the red seaweed Gracilaria sordida (Gracilariales)

α-1,4-Glucan phosphorylase (EC 2.4.1.1) from the red seaweed Gracilaria sordida (Harv.) W. Nelson was adsorbed onto starch-Sepharose 6B and Sephacryl S-300 under specified conditions. The algal enzyme was purified to homogeneity by these two steps. A molecular weight of 97.4 kDa was observed on SDS-polyacrylamide gel electrophoresis under reducing conditions, while the native molecular weight was 240 kDa asrevealed by 8-25% native gradient gel electrophoresis or 245 kDa by gel filtration. The pI of the enzyme was 5.4. It had a Km of 227, 264, 285, and 453 μg ml-1, respectively, towards glycogen, amylopectin, amylose, and maltodextrin. The enzyme activity was inhibited by cyclohexaamylose, ADP-glucose, and UDP-glucose. In contrast to other plant sources, cell-free extracts of G. sordida contained only one form of phosphorylase.     

Subcellular immuno-localization, amino acid composition and partial amino acid sequences of α-l,4-glucan phosphorylase of Gracilaria spp (Rhodophyta)

Antibodies have been raised against an α-l,4-glucan phosphorylase (EC 2. 4. 1. 1) purified from the red alga Gracilaria chilensis. Localization of α-l,4-glucan phosphorylase in thin sections of G. chilensis and G. tenuistipitata was performed using immuno-gold labelling and transmission electron microscopy. The enzyme was localized in the cytosol and around the cytosolic starch granules of the algal cells. The labelling was not associated with the chloroplast or the cell wall. Amino acid composition of the red algal phosphorylase was quite similar to that of potato tuber and rabbit muscle phosphorylases. Partial amino acid sequences showed 48, 54 and 65% homology with the rabbit, potato and Escherichia coli enzymes, respectively.     

The biosynthesis of phycocyanobilin in Anacystis nidulans

Aminolevulinic acid, the common precursor of linear and cyclic tetrapyrroles, can arise either by condensation of succinate and glycine or from the ent     

The role of modelling in the control of toxic blue-green algae

Blooms and scums of blue-green algae (cyanobacteria)have occurred throughout the world for many years andare only one of many problems associated withover-enrichment by nutrients of fresh and marinewaters. Although much studied and written about,eutrophication poses complex and difficult managementproblems. The role of modelling as an aid to thecontrol of blue green algae is discussed.     

Comparison of the long-wave chlorophyll fluorescence in various green and blue-green algae and diatoms

Two types of long-wave fluorescence bands with similar band shape occur at room temperature in various algae: F_II700 and F_I715. F_II700 occurs in a limited number of algae, follows PS II transients, increases with culture age and is moderately increased by cooling to 83 K. F_I715 occurs in most algae, especially Anabaena, but much less in most diatoms and Tribonema. It does not follow PS II transients, does not increase with culture age and is much increased by cooling to 83 K.An interpretation for the characteristics of F_II700 and F_I715 is given.     

A Historical Perspective for the Catalytic Reaction Mechanism of Glycosidase; So As to Bring about Breakthrough in Confusing Situation

Various catalytic reaction models have been proposed as the reaction mechanisms of glycosidases, but a reasonable and unitary model capable of interpreting both “inverting” and “retaining” glycosidase reactions remains to be established. As for the models proposed to date, the nucleophilic displacement mechanism and the oxocarbenium ion intermediate mechanism are widely known, but recently the former is widely accepted, and so the general tendency of world opinion appears to favor it. This reaction model, however, is considered to comprise some inconsistencies that cannot be neglected from the viewpoint of reactivity in organic chemistry. While the nucleophilic displacement mechanism is often applied to reactions of glycosidases, it appears unlikely that such reactions actually occur. This review argues that the oxocarbenium ion intermediate reaction mechanism is more rational than the nucleophilic displacement reaction mechanism, as the action mode of glycosidases and related enzymes.     

Cellulose and callose of the pollen tube wall of Camellia japonica

By chemical analyses in addition to IR spectroscopy and staining reactions, cellulose and a β-1,3-glucan (callose) were demonstrated to occur in the     

A greenhouse study on the effect of inoculation of N-fixing blue-green algae in an alluvial soil treated with P and Mo on the yield of rice and changes in the N-content of soil

Summary The efficiency of the inoculation of three cultures of N-fixing blue-green algaeviz. (i)Aulosira fertilissima (A₁), (ii)Nostoc muscorum (A₂) and (iii) their mixture (A₃) in increasing the grain and straw yield of rice, nitrogen uptake in grain and nitrogen content in soil was studied in a green house experiment with an alluvial soil in presence or absence of urea nitrogen application. Inoculation significantly increased the grain and straw yield of rice and nitrogen uptake in grain, but the efficiency of inoculation gradually decreased with the increase in the levels of urea nitrogen application, the extent of decrease varying with the algal cultures inoculated. The nitrogen content in the soils after the crop harvest recorded a significant increase due to inoculation but after air drying the soil a marker decrease of the same was observed, which indicated that most of the nitrogen added to the soil by blue-green algae through fixation did not persist after air drying the soil.     

Chemical composition of the cell walls of Lolium multiflorum endosperm

Cell walls isolated from Lolium multiflorum endosperm grown in liquid suspension culture contain 90% carbohydrate (as anhydro-glucose), 0·3 nitrogen, 1·9% lipid and 4·3% ash. The relative proportions of neutral sugars present in hydrolysates of the wall polysaccharides are glucose, 50%; arabinose, 19%; xylose, 26% and galactose, 5%. Extraction of the wall with 7 M urea solubilizes a polysaccharide representing 19% of the wall and composed of glucose and minor amounts of pentoses. This fraction has been examined by acid and enzymic hydrolysis and by periodate oxidation, and was shown to be a β-1,3; 1,4-glucan with approx. 79% 1,4-linkages. A specific β-glucan hydrolase has been used to determine the content of this mixed-linked glucan in isolated endosperm cell walls.     

铅对蟾蜍肝、肾过氧化物酶和酯酶同工酶的影响

以腹腔注射法对蟾蜍 (Bufobufogargarizans)给铅 ,处理 7d后 ,使用聚丙烯凝胶垂直平板电泳法 ,研究了不同浓度 (按铅计 1、2、4、8mg·kg-1 体重 )的铅对蟾蜍肝脏、肾脏过氧化物酶和酯酶同工酶的影响。结果表明 ,不同浓度的铅均可使肝、肾组织过氧化物酶同工酶带强弱发生明显变化 ;对肝、肾酯酶同工酶的影响表现出一定的组织差异性 ,且在一定范围内主要表现为应激性 ,即低剂量的铅可诱导酶活性的提高。     

Substrate specificity of E. coli uridine phosphorylase. Further evidences of high-syn conformation of the substrate in uridine phosphorolysis

Twenty five uridine analogues have been tested and compared with uridine with respect to their potency to bind to E. coli uridine phosphorylase. The kinetic constants of the phosphorolysis reaction of uridine derivatives modified at 2′-, 3′- and 5′-positions of the sugar moiety and 2-, 4-, 5- and 6-positions of the heterocyclic base were determined. The absence of the 2′- or 5′-hydroxyl group is not crucial for the successful binding and phosphorolysis. On the other hand, the absence of both the 2′- and 5′-hydroxyl groups leads to the loss of substrate binding to the enzyme. The same effect was observed when the 3′-hydroxyl group is absent, thus underlining the key role of this group. Our data shed some light on the mechanism of ribo- and 2′-deoxyribonucleoside discrimination by E. coli uridine phosphorylase and E. coli thymidine phosphorylase. A comparison of the kinetic results obtained in the present study with the available X-ray structures and analysis of hydrogen bonding in the enzyme-substrate complex demonstrates that uridine adopts an unusual high-syn conformation in the active site of uridine phosphorylase.     

Wave-related mortality in zygotes of habitat-forming algae from different exposures in southern New Zealand: the importance of ‘stickability’

Using field and laboratory experiments, we investigated the relative ability of zygotes of three species of habitat-forming large brown algae from southern New Zealand to survive wave action and remain attached after settling times of 1, 6, and 12 h. Zygotes of Hormosira banksii (Turner) Decaisne and Cystophora torulosa (R. Brown) J. Agardh, intertidal algae common on sheltered and semi-protected shores in southern New Zealand, had between 24% and 35% survival 1 h after settlement and exposed to a single wave in the lab and field. In contrast, Durvillaea antarctica (Chamisso) Hariot, an exposed-shore species, had up to 75% survival under the same conditions. Survival increased with post-settlement time for all three species. When given 6 h to attach under the same conditions, the survival of Hormosira and Cystophora zygotes ranged between 50% and 60% and between 80% and 90% when given 12 h to attach. Durvillaea, in contrast, had between 90% and 100% survival at both 6- and 12-h setting times. In other experiments, H. banksii and D. antarctica zygotes were given either 1, 6, or 12 h to attach and then placed for 12 h into sites within three levels of wave exposure (sheltered, intermediate and exposed). Survival of Hormosira zygotes given 1 and 6 h to attach was poor, ranging from 1% to 8%. If given 12 h to set, however, 5–8% of Hormosira zygotes survived, even at the exposed sites. Under similar conditions, Durvillaea survival was significantly higher, ranging from 70% to 100% at all post-settlement times, in sites of all exposures. Wave action clearly affects the ability of sheltered shore species to settle in exposed sites. However, our study highlights the importance of factors other than wave action in determining the distribution and abundance of post-settlement stages of D. antarctica across exposures.     

The consumption and utilization of the spiral blue-green algae Spirulina platensis in artificial diets by the silkworm, Bombyx mori

The consumption and utilization of various concentrations of the spiral blue-green algae, Spirulina platensis (Nordst.) Geitl., by the fourth-instar larvae of the silkworm, Bombyx mori L., was studied by incorporation into an artificial diet. The silkworms ingested more food on the low algal-powder diets, whereas they digested more efficiently on the high algal levels. The larvae fed on diets containing 30–40% algae had the shortest larval duration compared to those on low algal-powder diets. The freeze-dried powder of S. platensis is well utilized by B. mori larvae when added to artificial diets at levels between 15% and 30%, although the high algal content at 40% was slightly better for the efficiency of conversion of ingested diet into body substance (E.C.I.) and the cocoon production. However, analysis of the protein content in feces indicated an excess of the algal powder at 40%. Measurements of data on the food consumption and utilization in this study proposed that this spiral alga is dietetically utilizable as a protein source for rearing the silkworm in smaller quantities than on a soybean meal.

---

Resúmé La consommation et l'utilisation de différentes concentrations de Spirulina platensis par les chenilles de 4ème stade de Bombyx mori, ont été étudiées par incorporation dans un aliment artificiel. Les vers à soie ont ingéré plus d'aliment avec les régimes à faible concentration en algue, tandis qu'ils ont digéré plus efficacement les régimes à haute concentration d'algue. Les chenilles alimentées sur des régimes contenant 30 à 40% d'algue ont eu un développement larvaire plus bref que celles alimentées sur des régimes à faible concentration. La poudre congelée et séchée de S. platensis incorporée aux taux de 15 à 30% dans le régime artificiel est bien utilisée par les chenilles de B. mori, quoiqu'une teneur de 40% soit légèrement meilleure pour l'efficacité de conversion de l'aliment en matière vivante (E.C.I.) et la production de cocons. Cependant, l'analyse du contenu protéique dans les excréments révélait un excès de poudre d'algue à 40%. L'analyse des données au cours de cette étude, sur la consommation et l'utilisation des aliments, montre que S. platensis est utilisable diét étiquement en plus petite quantité que la farine de soja comme source de protéines pour l'élevage du ver à soie.

     

Further phloroglucinol derivatives in the fruits of Mallotus japonicus

Two new rottlerin-like phloroglucinol derivatives were detected from the fruits of Mallotus japonicus and identified as 3-(3,3-dimethylallyl)-5-(3-acetyl-2,4-dihydroxy-5-methyl-6-methoxybenzyl)-phlorobutyrophenone and -phloroisobutyrophenone by spectral studies. 2,6-Dihydroxy-3-methyl-4-methoxyacetophenone was also isolated     

Field and experimental studies on the combined impacts of cyanobacterial blooms and small algae on crustacean zooplankton in a large,eutrophic, subtropical,Chinese lake

Field and experimental studies were conducted to evaluate the combined impacts of cyanobacterial blooms and small algae on seasonal and long-term changes in the abundance and community structure of crustacean zooplankton in a large, eutrophic, Chinese lake, Lake Chaohu. Seasonal changes of the crustacean zooplankton from 22 sampling stations were investigated during September 2002 and August 2003, and 23 species belonging to 20 genera were recorded. Daphnia spp. dominated in spring but disappeared in mid-summer, while Bosmina coregoni and Ceriodaphnia cornuta dominated in summer and autumn. Both maximum cladoceran density (310 ind. l⁻¹) and biomass (5.2 mg l⁻¹) appeared in autumn. Limnoithona sinensis, Sinocalanus dorrii and Schmackeria inopinus were the main species of copepods. Microcystis spp. were the dominant phytoplankton species and formed dense blooms in the warm seasons. In the laboratory, inhibitory effects of small colonial Microcystis on growth and reproduction of Daphnia carinata were more remarkable than those of large ones, and population size of D. carinata was negatively correlated with density of fresh large colonial Microcystis within a density range of 0–100 mg l⁻¹ (r = −0.82, P< 0.05). Both field and experimental results suggested that seasonal and long-term changes in the community structure of crustacean zooplankton in the lake were shaped by cyanobacterial blooms and biomass of the small algae, respectively, i.e., colonial and filamentous cyanobacteria contributed to the summer replacement of dominant crustacean zooplankton from large Daphnia spp. to small B. coregoni and C. cornuta, while increased small algae might be responsible for the increased abundance of crustacean zooplankton during the past decades.     

Flow cytometric studies of the host-regulated cell cycle in algae symbiotic with green paramecium

Summary. Paramecium bursaria (green paramecium) possesses endosymbiotically growing chlorella-like green algae. An aposymbiotic cell line of P. bursaria (MBw-1) was prepared from the green MB-1 strain with the herbicide paraquat. The SA-2 clone of symbiotic algae was employed to reinfect MBw-1 cells and thus a regreened cell line (MBr-1) was obtained. The regreened paramecia were used to study the impact of the hosts growth status on the life cycle of the symbiotic algae. Firstly, the relationship between the timing of algal propagation and the host cell division was investigated by counting the algal cells in single host cells during and after the host cell division and also in the stationary phase. Secondly, the changes in the endogenous chlorophyll level, DNA content, and cell size in the symbiotic algae were monitored by flow cytometry and fluorescence microscopy. The number of algae was shown to be doubled prior to or during the host cell division and the algal population in the two daughter cells is maintained at constant level until the host cell cycle reenters the cytokinesis, suggesting that algal propagation and cell cycle are dependent on the hosts cell cycle. During the hosts stationary growth, unicellular algal vegetatives with low chlorophyll content were dominant. In contrast, complexes of algal cells called sporangia (containing 1–4 autospores) were present in the logarithmically growing hosts, indicating that algal cell division leading to the formation of sporangia with multiple autospores is active in the dividing paramecia.Correspondence and reprints: Graduate School of Environmental Engineering, University of Kitakyushu, 1-1 Hibikino, Wakamatsu-ku, 808-0135 Kitakyushu, Japan.