Arabinogalactan-proteins Degrading Enzymes

Abstract

Arabinogalactan proteins (AGPs) are a family of complex proteoglycans widely distributed in plants. They are found in the extracellular matrix associated with the plasma membrane and cell wall of higher plants. 1) AGPs are implicated in several aspects of cell wall biology including the signaling of cell context and cell expansion, yet remain elusive in terms of their mechanistic involvement in cell processes. 1 3) They are characterized by large amounts of carbohydrate components rich in galactose and L arabinose, and protein components rich in hydroxyproline. 3,4) Structural and immunochemical analyses reveal considerable heterogeneity to the arabinogalactan component, which can account for over 90% of AGP mass. The carbohydrate moieties of AGPs have a common structure consisting of a β 1,3 galactosyl backbone to which side chains of β 1,6 galactosyl residues are attached through O 6. L Arabinose and lesser amounts of other auxiliary sugars, such as glucuronic acid, L rhamnose, and L fucose, are attached to the side chains, usually at non reducing termini. 3,4) Gum arabic and larch arabinogalactan, which are a kind of AGP, are useful not only as food materials but also as food additives to improve the physical properties and the functionality of other food materials. 5 7) These are used as texture modifiers by themselves or with others and also used for stabilization of emulsions, suspension of particulates, control of crystallization, encapsulation, and formation of a film. 5 7) The excellent emulsifying properties are due to their AGP fraction in which the hydrophobic polypeptide backbone strongly absorbs at the oil water interface, while the attached carbohydrate moieties stabilize the emulsion.Glycoside hydrolases which have been classified into 112 families in the CAZy database (Carbohydrate Active enzymes server at http: www.casy.ort CAZY ) by their amino acid sequences, which strictly discriminate their substrates. 8 10) Therefore, it is possible to remove particular sugar residues and cleave the specific type of glycosidic linkages. Glycoside hydrolases capable of removing the carbohydrate moieties of AGPs would be useful tools to analyze or modify the structure and function of the carbohydrate moieties of AGPs; however, there has been limited research on such enzymes. In spite of the enzymes which act on the core β 1,3 , the β 1,6 galactan part of AGPs would be most important to degrade AGPs; no amino acid sequence for such enzymes has been reported. Recently, we have succeeded in the cloning of two kinds of galactanases, exo β 1,3 galactanase from Phanerochaete chrysosporium (Pc1,3Gal43A) and endo β 1,6 galactanase from Trichoderma viride (Tv6GAL) for the first time. 11,12) Here, we summarize the properties of both the exo β 1,3 galactanases and endo β 1,6 galactanases, which are key enzymes to degrade AGPs. Abstract: Arabinogalactan-proteins (AGPs) are a family of complex proteoglycans found throughout the plant kingdom. AGPs are massively glycosylated, and are implicated in diverse plant growth and...

Material Aspects of the Design and Operation of Direct Borohydride Fuel Cells

“…In this regard, the power densities of 32.8 and 35.4 mW cm -2 at 100 mA cm -2 , achieved using non-precious Ag and Ni anodes, respectively, were encouraging. The promising performance of the Ag cathode was attributed to its activity for oxygen reduction, which is a four-electron process in alkaline solution [27].…”

“…The MEA with the Pd/C cathode behaved similarly to that with the Pt/C but decreased more rapidly. The lower stability of the MEA with the Ag cathode was partially caused by the irreversible processes occurring at the Ag cathode surface, the cumulative effect led to gradual Ag deterioration [27]. The MEA with the Ni cathode exhibited a high initial performance but experienced faster deactivation than with the Ag/C, which may be due to hydride formation and hydrogen absorption [28,30,31].…”

Novel 3- O -α- d -Galactosyl-α- l -Arabinofuranosidase for the Assimilation of Gum Arabic Arabinogalactan Protein in Bifidobacterium longum subsp. longum

“…AGPs are found in normal human diet, such as in vegetables, fruits, and grains (16,17), and gum arabic AGP is commonly used as a food additive for emulsification and stabilization (18). Additionally, gum arabic AGP has been reported to increase the concentration of bifidobacteria in the descending colon, based on the results of studies conducted using a simulator of the human intestinal microbial ecosystem (19,20) and in vivo experiments in human subjects (21).…”