Microbial Levan

Han, Y. W.

doi:10.1016/s0065-2164(08)70244-2

Cited by 168 publications

(104 citation statements)

References 91 publications

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“…In general, glucans and/or fructans can be used as viscosifying, stabilizing, emulsifying, sweetening, gelling, or water-binding agents, in the food as well as in the nonfood industries (40,51,66,190,217,218). Certain oligosaccharides (e.g., fructooligosaccharides, isomaltooligosaccharides, and lactulose) and polysaccharides (e.g., fructans) are used as prebiotic food additives (14,15,50,84,151,164).…”

Section: Introductionmentioning

confidence: 99%

Structure-Function Relationships of Glucansucrase and Fructansucrase Enzymes from Lactic Acid Bacteria

Hijum

Kralj

Ozimek

et al. 2006

Microbiol Mol Biol Rev

390

315

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SUMMARY Lactic acid bacteria (LAB) employ sucrase-type enzymes to convert sucrose into homopolysaccharides consisting of either glucosyl units (glucans) or fructosyl units (fructans). The enzymes involved are labeled glucansucrases (GS) and fructansucrases (FS), respectively. The available molecular, biochemical, and structural information on sucrase genes and enzymes from various LAB and their fructan and α-glucan products is reviewed. The GS and FS enzymes are both glycoside hydrolase enzymes that act on the same substrate (sucrose) and catalyze (retaining) transglycosylation reactions that result in polysaccharide formation, but they possess completely different protein structures. GS enzymes (family GH70) are large multidomain proteins that occur exclusively in LAB. Their catalytic domain displays clear secondary-structure similarity with α-amylase enzymes (family GH13), with a predicted permuted (β/α)8 barrel structure for which detailed structural and mechanistic information is available. Emphasis now is on identification of residues and regions important for GS enzyme activity and product specificity (synthesis of α-glucans differing in glycosidic linkage type, degree and type of branching, glucan molecular mass, and solubility). FS enzymes (family GH68) occur in both gram-negative and gram-positive bacteria and synthesize β-fructan polymers with either β-(2→6) (inulin) or β-(2→1) (levan) glycosidic bonds. Recently, the first high-resolution three-dimensional structures have become available for FS (levansucrase) proteins, revealing a rare five-bladed β-propeller structure with a deep, negatively charged central pocket. Although these structures have provided detailed mechanistic insights, the structural features in FS enzymes dictating the synthesis of either β-(2→6) or β-(2→1) linkages, degree and type of branching, and fructan molecular mass remain to be identified.

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Section: Introductionmentioning

confidence: 99%

Structure-Function Relationships of Glucansucrase and Fructansucrase Enzymes from Lactic Acid Bacteria

Hijum

Kralj

Ozimek

et al. 2006

Microbiol Mol Biol Rev

390

315

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“…Apart some exceptions (van Hijum et al, 2003), bacterial fructans are of the levan type. They are much longer than plant fructans and are biosynthesized by levansucrases (Han, 1990). Besides having a role as a reserve component, fructans perhaps also ful®l more speci®c roles in plants and could contribute to drought resistance, frost tolerance or osmoregulation (Hendry, 1993;Hincha et al, 2000;Livingston and Henson, 1998;Vergauwen et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…Surprisingly, plant 1-FEHs apparently evolved from cell-wall-type and not from vacuolar invertases . Although both endoand exo-type 6-FEHs have been characterized and cloned from microorganisms (Han, 1990;Pereira et al, 2001), so far no 6-FEH cDNA has been cloned from any plant species.…”

Section: Introductionmentioning

confidence: 99%

Unexpected presence of fructan 6‐exohydrolases (6‐FEHs) in non‐fructan plants: characterization, cloning, mass mapping and functional analysis of a novel ‘cell‐wall invertase‐like’ specific 6‐FEH from sugar beet (Beta vulgaris L.)

et al. 2003

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SummaryAbout 15% of¯owering plant species synthesize fructans. Fructans serve mainly as reserve carbohydrates and are subject to breakdown by plant fructan exohydrolases (FEHs), among which 1-FEHs (inulinases) and 6-FEHs (levanases) can be differentiated. This paper describes the unexpected ®nding that 6-FEHs also occur in plants that do not synthesize fructans. The puri®cation, characterization, cloning and functional analysis of sugar beet (Beta vulgaris L.) 6-FEH are described. Enzyme activity measurements during sugar beet development suggest a constitutive expression of the gene in sugar beet roots. Classical enzyme puri®ca-tion followed by in-gel trypsin digestion and mass spectrometry (quadruple-time-of-¯ight mass spectrometry (Q-TOF) MS) led to peptide sequence information used in subsequent RT-PCR based cloning. Levantype fructans (b-2,6) are the best substrates for the enzyme, while inulin-type fructans (b-2,1) and sucrose are poorly or not degraded. Sugar beet 6-FEH is more related to cell wall invertases than to vacuolar invertases and has a low iso-electric point (pI ), clearly different from typical high pI cell wall invertases. Poor sequence homology to bacterial or fungal FEHs makes an endophytic origin highly unlikely. The functionality of the 6-FEH cDNA was further demonstrated by heterologous expression in Pichia pastoris. As fructans are absent in sugar beet, the role of 6-FEH in planta is not obvious. Like chitinases and bglucanases hydrolysing cell-surface components of fungal plant pathogens, a straightforward working hypothesis for further research might be that plant 6-FEHs participate in hydrolysis (or prevent the formation) of levan-containing slime surrounding endophytic or phytopathogenic bacteria.

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“…It is composed of dfructofuranosyl monomers linked by β(2 → 6) units and β(2 → 1) branches. The carbohydrate structure of Levan synthesized by different microorganisms is rather similar, while small differences appear in degree of polymerization and branching unit [128]. Its specificity is related to furanose form of carbohydrate conformation with an important role in molecule dissolution [129].…”

Section: Nanostructured Levan Thin Filmsmentioning

confidence: 99%

Biopolymer Thin Films Synthesized by Advanced Pulsed Laser Techniques

Axente¹,

Sima²,

Ristoscu³

et al. 2016

Recent Advances in Biopolymers

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This chapter provides an overview of recent advances in the field of laser-based synthesis of biopolymer thin films for biomedical applications. The introduction addresses the importance of biopolymer thin films with respect to several applications like tissue engineering, cell instructive environments, and drug delivery systems. The next section is devoted to applications of the fabrication of organic and hybrid organic-inorganic coatings. Matrix-assisted pulsed laser evaporation (MAPLE) and Combinatorial-MAPLE are introduced and compared with other conventional methods of thin films assembling on solid substrates. Advantages and limitations of the methods are pointed out by focusing on the delicate transfer of bio-macromolecules, preservation of properties and on the prospect of combinatorial libraries' synthesis in a single-step process. The following section provides a brief description of fundamental processes involved in the molecular transfer of delicate materials by MAPLE. Then, the chapter focuses on the laser synthesis of two polysaccharide thin films, namely Dextran doped with iron oxide nanoparticles and Levan, followed by an overview on the MAPLE synthesis of other biopolymers. The chapter ends with summary and perspectives of this fast-expanding research field, and a rich bibliographic database.

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Microbial Levan

Cited by 168 publications

References 91 publications

Structure-Function Relationships of Glucansucrase and Fructansucrase Enzymes from Lactic Acid Bacteria

Structure-Function Relationships of Glucansucrase and Fructansucrase Enzymes from Lactic Acid Bacteria

Unexpected presence of fructan 6‐exohydrolases (6‐FEHs) in non‐fructan plants: characterization, cloning, mass mapping and functional analysis of a novel ‘cell‐wall invertase‐like’ specific 6‐FEH from sugar beet (Beta vulgaris L.)

Biopolymer Thin Films Synthesized by Advanced Pulsed Laser Techniques

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