海藻非蛋白质氨基酸的研究进展

海藻非蛋白质氨基酸是海藻中一类重要的生物活性物质,大多具有清热、解毒、驱虫、降血压、防癫痫等功能,本文主要对海藻非蛋白质氨基酸的概念、分类、生物合成、生物功能及其应用、检测分析、分离提取等做一概述,为更好的开发利用这类生物活性物质提供参考.     

Photosynthetic marine organisms as a source of anticancer compounds

Since early human history, plants have served as the most important source of medicinal natural products, and even in the “synthetic age” the majority of lead compounds for pharmaceutical development remain of plant origin. In the marine realm, algae and seagrasses were amongst the first organisms investigated by marine natural products scientists on their quest for novel pharmaceutical compounds. Forty years after the pioneering work in the field of marine drug discovery began, the biodiversity of marine organisms investigated as potential sources of anticancer, anti-inflammatory, and antibiotic compounds has increased tremendously. Nonetheless, marine plants are still an important source of novel secondary metabolites with interesting biomedical properties. The present review focuses on the antitumour properties of compounds isolated from marine algae, phytoplankton, mangroves, seagrasses, or cordgrasses. Compounds produced by marine epi- or endophytic fungi are also discussed.     

Filamentous tropical marine cyanobacteria: a rich source of natural products for anticancer drug discovery

A plethora of structurally novel bioactive secondary metabolites have been reported from the prokaryotic filamentous marine cyanobacteria in the past few decades. In addition to the production of harmful toxins, these marine blue-green algae are emerging as an important source of anticancer drugs. The majority of these potent biomolecules, including the dolastatins, curacin A, hectochlorin, the apratoxins, and the lyngbyabellins, belongs to the mixed polyketide–polypeptide structural class. Furthermore, a high proportion of these natural products target eukaryotic cytoskeleton, such as tubulin and actin microfilaments, making them an attractive source of potential anticancer drugs. In recent years, a number of potent marine cyanobacteria have also been reported to modulate cell death and apoptosis in cancer cells as well as target enzymes such as histone deacetylase. A number of marine cyanobacterial compounds have also served as structural templates for the generation of new drug leads, further attesting to the importance of these marine microbes as an important source of new pharmaceuticals. This review serves to highlight the chemistry and biology of selected anticancer marine cyanobacterial natural products exhibiting significant biological activities in the nanomolar or submicromolar range, and their discussion will be based on the different modes of action.     

Sulfur and phytoplankton: acquisition, metabolism and impact on the environment

Sulfur emission from marine phytoplankton has been recognized as an important factor for global climate and as an entry into the biogeochemical S cycle. Despite this significance, little is known about the cellular S metabolism in algae that forms the basis of this emission. Some biochemical and genetic evidence for regulation of S uptake and assimilation is available for the freshwater model alga Chlamydomonas. However, the marine environment is substantially different from most fresh waters, containing up to 50 times higher free sulfate concentrations and challenging the adaptive mechanisms of primary and secondary S metabolism in marine algae. This review intends to integrate ecological and physiological data to provide a comprehensive view of the role of S in the oceans.     

Photoheterotrophy in the production of phytoplankton organisms

Interest is growing in algae as sources of medicinal and other potentially useful compounds, as well as their use in fish rearing. We are interested in their production of polyunsaturated fatty acids (PUFA). Photoautotrophic growth gives the highest levels of unsaturation in the fatty acid pool, but biomass concentrations are low. Heterotrophy on sugars gives higher biomass but seems to give more saturation in the fatty acids. In freshwater algae acetate has proved to be a good carbon source for photoheterotrophic growth, giving a crop with reasonably high levels of PUFA. In addition it is possible to regulate acetic acid addition through the pH change as acetate is used up in a well-aerated system, so achieving high biomass yields in the presence of relatively low acetate concentration. When we attempted to extend this to marine algae (principally species used in fish farming), we found that acetic acid was ineffective or sometimes toxic to most species tested, even at high pH. However, glycerol stimulated growth in a number of the algae. We report on this stimulation, and on the fatty acid composition of the resulting algal crop, discuss the problems in regulating the addition of this metabolite to algal cultures, and speculate on applications in the production of other useful algal metabolites. We also show that some of these algae used in fish farming grow best when the salinity of the water is rather less than that found in standard sea water.     

Blue-green algae (cyanobacteria): prospects and perspectives

Summary Photosynthetic, prokaryotic blue-green algae (cyanobacteria) occur in a wide range of natural habitats of diverse ionic composition and as such, represent an important source of biological material for biosolar energy conversion programs using saline water. The gasvacuolate, filamentous Spirulina is grown in seminatural culture in Lake Texcoco, Mexico, as a major source of single-cell protein for animal nutrition. Pilot-scale trials in other areas of the world have also demonstrated the suitability of blue-green algae, including Spirulina, for growth under brackish conditions. The carbohydrate accumulation profiles of blue-green algae differ in isolates from freshwater, marine and hypersaline habitats, with a trend towards sucrose or trehalose accumulation in stenohaline freshwater strains grown in media containing NaCl, while euryhaline and marine forms frequently accumulate glucosylglycerol. Many halotolerant isolates from hypersaline habitats accumulate glycinebetaine in response to osmotic stress. This knowledge may provide scope for future improvement in the N₂ fixation rates of blue-green algae in saline media, using betaine-accumulating N₂-fixing strains in preference to other, saltsensitive isolates.     

Biology and systematics of heterokont and haptophyte algae

In this paper, I review what is currently known of phylogenetic relationships of heterokont and haptophyte algae. Heterokont algae are a monophyletic group that is classified into 17 classes and represents a diverse group of marine, freshwater, and terrestrial algae. Classes are distinguished by morphology, chloroplast pigments, ultrastructural features, and gene sequence data. Electron microscopy and molecular biology have contributed significantly to our understanding of their evolutionary relationships, but even today class relationships are poorly understood. Haptophyte algae are a second monophyletic group that consists of two classes of predominately marine phytoplankton. The closest relatives of the haptophytes are currently unknown, but recent evidence indicates they may be part of a large assemblage (chromalveolates) that includes heterokont algae and other stramenopiles, alveolates, and cryptophytes. Heterokont and haptophyte algae are important primary producers in aquatic habitats, and they are probably the primary carbon source for petroleum products (crude oil, natural gas).     

Structure, biology, evolution, and medical importance of sulfated fucans and galactans

Sulfated fucans and galactans are strongly anionic polysaccharides found in marine organisms. Their structures vary among species, but their major features are conserved among phyla. Sulfated fucans are found in marine brown algae and echinoderms, whereas sulfated galactans occur in red and green algae, marine angiosperms, tunicates (ascidians), and sea urchins. Polysaccharides with 3-linked, beta-galactose units are highly conserved in some taxonomic groups of marine organisms and show a strong tendency toward 4-sulfation in algae and marine angiosperms, and 2-sulfation in invertebrates. Marine algae mainly express sulfated polysaccharides with complex, heterogeneous structures, whereas marine invertebrates synthesize sulfated fucans and sulfated galactans with regular repetitive structures. These polysaccharides are structural components of the extracellular matrix. Sulfated fucans and galactans are involved in sea urchin fertilization acting as species-specific inducers of the sperm acrosome reaction. Because of this function the structural evolution of sulfated fucans could be a component in the speciation process. The algal and invertebrate polysaccharides are also potent anticoagulant agents of mammalian blood and represent a potential source of compounds for antithrombotic therapies.     

Marine algae as a potential pharmaceutical source for anti-allergic therapeutics

The prevalence of allergic diseases such as asthma, atopic dermatitis, and allergic rhinitis has increased during the last two decades and contributed a great deal to morbidity and an appreciable mortality in the world. Until now, few novel efficacious drugs have been discovered to treat, control or even cure these diseases with a low adverse-effect profile. Meanwhile, glucocorticoids are still the mainstay for the treatment of allergic disease. Therefore, it is necessary to isolate novel anti-allergic agents from natural resources. Recently, marine algae have received much attention as they are a valuable source of chemically diverse bioactive compounds with numerous health benefit effects. This review focuses on anti-allergic agents derived from marine algae and presents an overview of their pharmaceutical potential in the treatment of allergic disorders.     

Drug Discovery from Marine Microbes

The marine environment has been a source of more than 20,000 inspirational natural products discovered over the past 50 years. From these efforts, 9 approved drugs and 12 current clinical trial agents have been discovered, either as natural products or as molecules inspired from the natural product structure. To a significant degree, these have come from collections of marine invertebrates largely obtained from shallow-water tropical ecosystems. However, there is a growing recognition that marine invertebrates are oftentimes populated with enormous quantities of “associated” or symbiotic microorganisms and that microorganisms are the true metabolic sources of these most valuable of marine natural products. Also, because of the inherently multidisciplinary nature of this field, a high degree of innovation is characteristic of marine natural product drug discovery efforts.     

Diversity and biotechnological potential of the sponge-associated microbial consortia

Sponges are well known to harbor diverse microbes and represent a significant source of bioactive natural compounds derived from the marine environment. Recent studies of the microbial communities of marine sponges have uncovered previously undescribed species and an array of new chemical compounds. In contrast to natural compounds, studies on enzymes with biotechnological potential from microbes associated with sponges are rare although enzymes with novel activities that have potential medical and biotechnological applications have been identified from sponges and microbes associated with sponges. Both bacteria and fungi have been isolated from a wide range of marine sponge, but the diversity and symbiotic relationship of bacteria has been studied to a greater extent than that of fungi isolated from sponges. Molecular methods (e.g., rDNA, DGGE, and FISH) have revealed a great diversity of the unculturable bacteria and archaea. Metagenomic approaches have identified interesting metabolic pathways responsible for the production of natural compounds and may provide a new avenue to explore the microbial diversity and biotechnological potential of marine sponges. In addition, other eukaryotic organisms such as diatoms and unicellular algae from marine sponges are also being described using these molecular techniques. Many natural compounds derived from sponges are suspected to be of bacterial origin, but only a few studies have provided convincing evidence for symbiotic producers in sponges. Microbes in sponges exist in different associations with sponges including the true symbiosis. Fungi derived from marine sponges represent the single most prolific source of diverse bioactive marine fungal compounds found to date. There is a developing interest in determining the true diversity of fungi present in marine sponges and the nature of the association. Molecular methods will allow scientists to more accurately identify fungal species and determine actual diversity of sponge-associated fungi. This is especially important as greater cooperation between bacteriologists, mycologists, natural product chemists, and bioengineers is needed to provide a well-coordinated effort in studying the diversity, ecology, physiology, and association between bacteria, fungi, and other organisms present in marine sponges.     

Cultivation of Microorganisms in the Cultural Medium Made from Squid Internal Organs and Accumulation of Polyunsaturated Fatty Acids in the Cells

The disposal and more efficient utilization of marine wastes is becoming increasingly serious. A culture media for microorganisms has been prepared from squid internal organs that are rich in polyunsaturated fatty acids (PUFAs). Both freshwater and marine bacteria grew well in this medium and some bacteria accumulated PUFAs in their lipids, suggesting uptake of exogenous PUFAs. Higher PUFA accumulations were observed in Escherichia coli mutant cells defective either in unsaturated fatty acid biosynthesis or fatty acid degradation, or both, compared to those without these mutations. Therefore, PUFA accumulation in cells can be improved by genetic modification of fatty acid metabolism in the bacteria. Squid internal organs would be a good source of medium, not only for marine bacteria but also for freshwater bacteria, and that this process may be advantageous to make efficient use of the fishery wastes and to produce PUFA-containing microbial cells and lipids.     

Chlororespiration in Green Algae Isolated From Desert Crusts

Photosynthetic organisms enduring extreme temperatures, low water availability, or high light require photoprotective mechanisms to prevent sustained damage to photosynthetic machinery. Green microalgae living in desert crust communities of the south‐western US experience all these environmental stresses, yet photophysiological studies of green algae in the literature have focused on only a handful of common aquatic and marine species. We are examining the variation in green algal photoprotective mechanisms that is the result of natural selection acting independently in multiple lineages of highly diverse desert green algae (Chlorophyta) within the classes Chlorophyceae and Trebouxiophyceae. We have found that unusually extensive dark reduction of the plastoquinone pool is a prominent photophysiological feature among these desert algae; this reduction may be linked with enhanced chlororespiration. Recently, chlororespiration in higher plants has been linked through mutant analysis to control of the carotenoid synthetic pathway, heat stress, and starch metabolism among other pathways, though the function of chlororespiration remains controversial. Given that green algae and higher plants are monophyletic, analysis of potential chlororespiration in desert green algae may help decipher the evolution of the chlororespiratory process as well as its potential role in photoprotection in desert habitats.     

Synthesis enables identification of the cellular target of leucascandrolide A and neopeltolide

Leucascandrolide A and neopeltolide are structurally homologous marine natural products that elicit potent antiproliferative profiles in mammalian cells and yeast. The scarcity of naturally available material has been a significant barrier to their biochemical and pharmacological evaluation. We developed practical synthetic access to this class of natural products that enabled the determination of their mechanism of action. We demonstrated effective cellular growth inhibition in yeast, which was substantially enhanced by substituting glucose with galactose or glycerol. These results, along with genetic analysis of determinants of drug sensitivity, suggested that leucascandrolide A and neopeltolide may inhibit mitochondrial ATP synthesis. Evaluation of the activity of the four mitochondrial electron transport chain complexes in yeast and mammalian cells revealed cytochrome bc(1) complex as the principal cellular target. This result provided the molecular basis for the potent antiproliferative activity of this class of marine macrolides, thus identifying them as new biochemical tools for investigation of eukaryotic energy metabolism.     

Uric acid deposits in symbiotic marine algae

The symbiosis between cnidarians and dinoflagellate algae is not understood at the cell or molecular level, yet this relationship is responsible for the formation of thousands of square kilometres of coral reefs. We have investigated the nature of crystalline material prominent within marine algal symbionts of Aiptasia sp. anemones. This material, which has historically been considered to be calcium oxalate, is shown to be uric acid. We demonstrate that these abundant uric acid stores can be mobilized rapidly, thereby allowing the algal symbionts to flourish in an otherwise N-poor environment. This is the first report of uric acid accumulation by symbiotic marine algae. These data provide new insight and considerations for understanding the physiological basis of algal symbioses, and represent a new and previously unconsidered aspect of N metabolism in cnidarian, and a variety of other, marine symbioses.     

Bio-mining the microbial treasures of the ocean: new natural products

The biological resources of the oceans have been exploited since ancient human history, mainly by catching fish and harvesting algae. Research on natural products with special emphasis on marine animals and also algae during the last decades of the 20th century has revealed the importance of marine organisms as producers of substances useful for the treatment of human diseases. Though a large number of bioactive substances have been identified, some many years ago, only recently the first drugs from the oceans were approved. Quite astonishingly, the immense diversity of microbes in the marine environments and their almost untouched capacity to produce natural products and therefore the importance of microbes for marine biotechnology was realized on a broad basis by the scientific communities only recently. This has strengthened worldwide research activities dealing with the exploration of marine microorganisms for biotechnological applications, which comprise the production of bioactive compounds for pharmaceutical use, as well as the development of other valuable products, such as enzymes, nutraceuticals and cosmetics. While the focus in these fields was mainly on marine bacteria, also marine fungi now receive growing attention. Although culture-dependent studies continue to provide interesting new chemical structures with biological activities at a high rate and represent highly promising approaches for the search of new drugs, exploration and use of genomic and metagenomic resources are considered to further increase this potential. Many efforts are made for the sustainable exploration of marine microbial resources. Large culture collections specifically of marine bacteria and marine fungi are available. Compound libraries of marine natural products, even of highly purified substances, were established. The expectations into the commercial exploitation of marine microbial resources has given rise to numerous institutions worldwide, basic research facilities as well as companies. In Europe, recent activities have initiated a dynamic development in marine biotechnology, though concentrated efforts on marine natural product research are rare. One of these activities is represented by the Kieler Wirkstoff-Zentrum KiWiZ, which was founded in 2005 in Kiel (Germany).     

海藻酸盐裂解酶研究进展

海藻酸盐裂解酶是一类降解褐藻中海藻酸盐的酶。此酶已经在多种有机体中得到分离。对海藻酸盐裂解酶的生物特性、研究方法及其生物学功能进行了介绍。在酶学特性研究的基础上 ,通过酶解构建新型海藻酸盐多聚物 ,可增强和扩展海藻酸盐裂解酶在工业、农业、医药领域中的应用 ,使其在海藻多糖的高值化应用中发挥重要的作用。概述了海藻酸盐和海藻酸盐裂解酶过去和现在的研究状况 ,展望了海藻酸盐和海藻酸盐裂解酶将来的应用前景。