D-Galacturonic acid

Another microbial polysaccharide-based emulsifier is Hposan, produced by the yeast Candida lipolytica when grown on hydrocarbons (223). Liposan is apparentiy induced by certain water-immiscible hydrocarbons. It is composed of approximately 83% polysaccharide and 17% protein (224). The polysaccharide portion consists of D-glucose, D-galactose, 2-amino-2-deoxy-D-galactose, and D-galacturonic acid. The presence of fatty acyl groups has not been demonstrated the protein portion may confer some hydrophobic properties on the complex. 

Deoxy-sugars. Part XXI. Synthesis of Some Derivatives of 2-Deoxy-D-galacturonic Acid, W. G. Overend, F. Shafizadeh, and M. Stacey, J. Chem. Soc., (1951) 1487-1489. 

Pectin belongs to a family of plant polysaccharides in which the polymer backbone consists of (1— 4)-linked a-D-galacturonic acid repeating-units. Often, (1— 2)-linked a-L-rhamnose residues interrupt the regular polygalacturonate sequence. The high viscosity and gelling properties of pectins are exploited by the food and pharmaceutical industries. X-Ray studies on sodium pectate, calcium pectate, pectic acid, and pectinic acid (methyl ester of pectic acid) have disclosed their structural details. 

The LPS from Proteus species contain amino acids linked as amides to acidic sugars. Thus, L-lysine is linked by way of N-6 to a D-galacturonic acid residue (52) in the LPS from P. hauseri, but by way of N-2 to a D-glucu-ronic acid residue in the LPS from P. mirabilis 027. The latter LPS also contains L-alanine, linked to the carboxyl group of a D-galacturonic acid residue. 

The substrate for HGA synthesis is UDP-D-galacturonic acid (UDP-GalA) (81). UDP-GalA has been isolated from plants (59) and several pathways for its synthesis in planta have been reported (31). In vitro studies on pectin biosynthesis have been hampered since radiolabeled UDP-galacturonic acid is not commercially available. Previous researchers have used several... 

Mitcham, E.J., Gross, K.C., and Wasserman, B.P. (1991) Synthesis of uridinediphospho-[U- C]-D-galacturonic acid by enzyme particulate fractions and purification via high performance liquid chromatography. Phytochem.Anal. 2 112-115. 

In the course of studies on the physicochemical properties of natural polymers in aqueous solution, attention has been drawn to pectic acid, i.e. poly (a-D)galacturonic acid as a potential model of a rigid polysaccharide. 

Extensive data are given in the Uterature for the potentiometric titration of polymer acids which may be used to study the behaviour of polyelectrolyte systems under different conditions. For poly(a-D) galacturonic acid there are few data of this kind, especially in connection with the occurrence of a conformational transition induced by pH variations, or with the effect brought about by the addition or the exchange of counterions. Since for a polyacid not exhibiting a conformational transition in the course of titration, pK K denoting the apparent dissociation constant) increases monotonously with degree... 

The purpose of this study is to consider in more detail the influence of the size and nature of the counterion on the degree and extent of dissociation of poly(a-D)galacturonic acid already discussed in a previous paper [2], particularly to check the effect of screening the charges on the polyacid in the presence of different counterions. 

Commercially available poly(a-D)galacturonic acid PGA) was purchased from Fluka Chemie. To obtain an aqueous solution of the polyacid, insoluble PGA was converted to its soluble sodium salt and then percolated through a cation-exchange resin in the H-form [3]. 

The partial specific volume of the monomeric unit in PGA was found to be approximately 3 per cent higher than the value of D-galacturonic acid... 

Characteristics of fraction I. The carbohydrate content of Fraction I was 84.4 %, in which the main component is D-galacturonic acid (71 %). Consequently, the polysaccharide is of a pectic type. The neutral sugars accounted for 13.4 % and according to their qualitative composition (Table 2) they correspond to the composition of pectin, isolated from sunflower heads (18). It is worth noting the high content of L-arabinose and D-galactose, compared with the other monosaccharides. The protein content was 7.8 %. 

Fractions Total volume/eluate, ml D-galactu- neutral sugars, ronic acid, mg D-glucose mg protein, mg D-galacturonic acid % neutral sugars % protein content, %... 

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