Glycolipids: Function and Structure
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Published: Tue, 05 Jun 2018
Marine fungi are saprophytic or heterotrophic form of filamentous spore forming eukaryote microorganisms are extensively lives in the marine or estuarine ecosystem. The characterization and diversity of the marine fungi can be studied by the direct observation of morphological structure and next generation sequencing. Taxonomically characterized marine fungi are belongs to either facultative or obligate forms. Facultative forms are originally sourced from terrestrial or fresh water region but they are able to colonize and adopt with the marine habitat and the obligate are extensively live in marine ecosystem (Kohlmeyer and Kohlmeyer, 1979). The fungi are extensively reported for the several biotechnological applications industrial utilization in enzymes, natural products and agriculture biocontrol etc.
The marine fungus are taxonomically distinct (Jones et al., 2009), saline tolerant (Jennings, 1986), special biochemical properties (Damare et al., 2006). Interestingly, the marine fungi have the novelty than the obligate fungi and attracts in applications of omics (Damare et al., 2012). Generally, marine fungi can be isolated from the nutrient rich substrata such as decaying wood (harbour), coral reef (Le Campion- Alsumard et al., 1995), seagrases (Thirunavkkarasu, 2011) and mangrove ecosystem (Saravanakumar et al., 2012) and deep sea soil (Damare, 2007) are enhance distinct diversity of the obligate fungi (Sridhar, 2005). Among the marine substrate, mangrove is an second largest source for the isolation of obligate marine fungi (Ragukumar 2004). However, the biotechnological application of marine fungi differs with the terrestrial fungi due to their environmental adaptations and distributions. Many research focus on biotechnological utilization of natural products, enzymes, biocontrol, bioremediation, fuel conservation, waste management by using the marine fungi. A lot of structurally and pharmaceutically novel metabolites, isolated from marine fungi. However, this article focuses the glycollipids from the marine fungi and their properties, biological functions and applications.
Glycolipids are a structurally very heterogenous group of membrane bound compound present in all living prokaryotic and eukaryotic organisams to human cells. The term of “glycolipid” is a compound contains one or more monosaccharides glycodidically linked in to a lipid (Brandenburg and Holst, 2005). Glycolipids are an essential constituent of cellular membrane and have the remarkable biological functions of cell aggregation or dissociation act as receptor of accepter to provide the contact. Several glycolipids has important role in immune system.
The glycolipids are interesting group of the compound occurred in cell wall of animals, microbes and plant sources (Pinto et al., 2008). The fungal glycolipids are composed of a sugar units usually glucose and galatose, hydrophobic ceramides, C19 sphingoid, C-9 metyl braches and unsaturated linkages with hydroxyhexadecanoic acids (Pinto et al., 2008).
Glycoconjugates in fugal cell wall
Glycoconjugates are composed of glycoprotins, peptides, glucons, polysaccharides, phosphoric acid, phospholipids, nitrogen and glycolipid molecules and found in the cell wall. Among the defining characteristics of fungal is cell wall complex architecture. Fungal cell walls are substantially thicker than bacterial cell walls and normally make up 10-30% of the biomass. They are freely permissible to small molecules and solute transport system and signalling receptors remains in cell membrane. A different cell wall found in the fungi comparing to animals and the role of these walls includes osmotic support, selective permeability and interaction with environment (Conzalexz et al., 2009). Fungal walls consist of covalently cross linked polysaccharides of β-glycans and Chitin and several polysaccharides are covalently cross linked through glycosidic bonds (Pinto et al., 2008).
Fungal glycolipids exterior
Generally, the glycolipid molecules are found in cell membrane of all eukaryotic cell membranes, are contain the sugar called as glycolipids besides biologically produced biosurfactants are called as glycolipids. However, all type of glycolipids are biosurfactants but not all the biosurfactants are glycolipids (Mukherjee et al., 2006; Khopade et al., 2012). Simplest glycolipids contain the one or more sugars (Fig.) and complex glycolipids such as gangliosides contain a branch chain with several sugars. Cell membranes of the fungi have the many types membrane and are assembled from four compounds such as (i) phospholipids molecules, (ii) transmembrane proteins, (iii) inerter protein network, and (iv) cell surface markers are not identical. The glycolipids are formed in the cell wall of fungi by glycosylation in endoplasimic reticulam (ER) membrane sections and transfer the Golgi complex followed by plasma membrane (Fig). These add the sugar molecules chain to lipids called the sugar coating lipids that extents the outside of fungal cells and differences were identified in glycolipids among fungal species and used as cell surface layer or marker besides glycolipids are also compound of the fatty acids contain carbohydrates, and nitrogen not phosphoric acids includes the certain compounds of the gangliosides, sulfolipids and salfatids (Pinto et al., 2008). The glycolipids are a marker for the cell identification of cell surface changes and are serving as fundamental building blocks of fungi, energy molecule or store, component of membrane constituents, signal molecule to interact the environmental compounds in through outer matrix, lectins, growth factor, and a potential factor of pathogenesis and immune responses (Hakomori, 1990; Springer and Lasky, 1991; Pinto et al., 2008). Moreover, the detail mechanism of role and properties of the glycolipids in fungus remain unclear.
Marine fungal glycolipids
Research on glycolipids from the marine resources has expanded the due attention due to its potential novelty in biotechnological applications. Muralidhar et al., (2003) have been reviewed the glycolipids from the marine resources such as algae (Lo et al., 2001), microorganisms: bacteria (Batrakov et al., 1998), fungi (Abraham et al., 1994), yeasts (Zinjarde and pant, 2002), actionbacteria (Kokare et al., 2007), sponges (pettit et al., 1999), gorgonians (Shin and Seo, 1995), sea anemones (Sugita et al., 1994), bryozoans (Ojika et al., 1997), tunicates (Loukaci et al., 2000), marine annelid (Noda et al., 1992), star fish (Sugiyama et al., 1988), sea cucumber (Higuchi et al., 1994), sea urchin (Babu et al., 1997) crinoids (Arao et al., 1999), molluscs (Yamaguchi et al., 1992), and marine crab (Asai et al., 2000).
In terrestrial Fungus, in general yeasts have glycolipids as major constituents and are not the major compound in more fungal species. However, a high Glycolipids content of 11-16% of total lipids in Blastocladiella emersonii, the major compound of glycollipid is GalDAG and Gal2DAG (Mills and Cantino, 1974). The 61- 48 % of glycolipids is found in mycelia of Macrophomina phaseoline and the lower in the sclerotia (14-62%). However the glycolipids concentrations varied according the constituents of fermentation medium. The major compound of the fungal glycolipids identified as GalDAG and Gal2DAG based structural characterization. Further the major glycolipids of fungi is glycosphingolipids and D- glucosylceramides (Weete, 1980). Galactocerebrosides has been found in fungal species, of Aspergillus miger, C.utilis and S. cerevisae (Wagner and Zofcsik, 1969). Besides the fungal species Fusarium lini, Phycomycetes blakesleeanus and mushrooms are known to produce the glycolipids (Weiss et al., 1973). Subsequently, the glycolipids are widely studied from Torulaspora delbruecki , Saccharomyes cerevisae, Candida glabrata, Kluyveromyes yarrowii, F. pedrosoi and K. polyporus (Saito et al., 2006 ; Pinto et al., 2008). The long chain sphingadinene has been first reported from Aspergillus oryzae (Fujino and Ohishi, 1976) and subsequently from Schizophyllum commune (Ballio et al., 1979), Fusicoccum amygdale (Ballio et al., 1979)), Clitocybe geotrope and Aspergillus fumigatus (Villas Boss et al., 1994), C. nebularis (Fodegel et al., 1986), A. niger(levery et al., 2000), A. versicolor (Walenkamp et al., 1999), Candida albicans (Matsubara et al., 1987), Acremonium chrysogenum (Sakaki et al., 2001), Cryptococcus neoformans (Rodrigues et al., 2000), Colletotrichum gloeosporioides ( de Silva et al., 2004), Fonsecaea pedrosoi (Nimrichter et al., 2005), Hansenula anomala (Ng et al., 1977), Fusarium sp. (Duarte et al., 1998), Histoplasma capulatum (Toledo et al., 2001), Kluyeromyces waltii (Takakuwa et al., 2002), paracoccidioides brasiliensis (Takahahi et al., 1996), Magnaporthe grisea (Koga et al., 2006), Pichia pastoris (Sakaki et al., 2001), Saccharomyces klyuyveri (Takakuwa et al., 2002), Pseudallescheria boydii (Pinto et al., 2002), Termitomyces albuminosus (Qi et al., 2002) Sporothrix schenkii (Toledo et al., 2001).
In marine fungi, very few studies are available on glycolipids of marine fungi (Table.1); the marine white rot marine fungi Nia vibrissae is producer of glycolipids with inhibitory activity, the binding of endotoxin Lipopolysaccharide (LPS) to human endotoxin receptor (Helmholz et al., 1999). Marine fungi Gliocladium roseum KF-1040 is a producer of Roselipins can inhibit the enzyme diacylglycerol acyl transferase (Omura et al., 1999; Tomada et al., 1999; Tabata et al., 1999). Glycolipids derived from marine yeasts Calyptogena soyoae, Yarrowia lipolytica are effective on degradation of hydrocarbon (Zinjarde and pant, 2002; Konishi et al., 2010). Glycolipids synthesised form filamentous endosymbiotic Aspergillus ustus has the significant antimicrobial activity (Kiran et al., 2009). Several marine fungus such as Penicillum sp. F23-2 (Sun et al., 2009), Linincola laevis (Abraham et al., 1994), Fusarium sp (Li et al., 2002) and Microsphaeropsis olivacea (Keugen et al., 1996) are significantly produced the glycolipids with unknown application.
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