Search PubMed⌕ Search

Biomedical subjects

I W Sutherland

Publications and source records attributed to I W Sutherland.

At least 55 records · Page 3Linked to original sources
PubMed1976

The butanol-soluble proteins of Klebsiella aerogenes.

Membranes of Klebsiella aerogenes were extracted with acid butanol at pH 4.2 and the solubilized proteins were fractionated by precipitation at 0 degrees C and -20 degrees C. The -20 degrees C precipitate was examined by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. Several enzyme activities associated with polysaccharide biosynthesis have been identified in the crude -20 degrees C precipitate and an attempt was made to separate the enzymes from other protein. The role of certain of these enzymes in a control mechanism for polysaccharide synthesis in K. aerogenes has been postulated.

Amino Acids↗
PubMed1975

Comparison of polysaccharides produced by Myxococcus strains.

Exopolysaccharides were prepared from cultures of four Myxococcus strains grown on solid and in liquid media, and also from the fruiting bodies. Lipopolysaccharides could be extracted with aqueous phenol from the vegetative bacteria, but were absent from microcysts. Mannose and D-glucose were present in all the exopolysaccharides and three of the lipopolysaccharides examined. Other monosaccharides identified in the exopolysaccharides were D-galactose, N-acetylglucosamine and N-acetylgalactosamine. The composition of the lipopolysaccharides was more complex than that of the exopolysaccharides and, in addition to the neutral hexoses and amino sugars, rhamnose was identified in two preparations and ribose in another. No lipopolysaccharide preparations contained O-methyl xylose or heptose. The polysaccharides secreted by the bacillary forms grown on solid or in liquid media closely resembled the polysaccharides isolated from the fruiting bodies, in which they provided a matrix surrounding the microcysts. Each pair of polysaccharides contained the same monosaccharides, although in slightly different proportions. Differences were found in preparations from different strains. These results suggest that in the development cycle of the genus Myxococcus, considerable use is made of pre-existing enzyme systems to synthesize the precursors necessary for polysaccharide synthesis. Any specific difference between the polysaccharide produced by the bacilli and that surrounding the microcysts may lie in the fine structure, rather than in the individual components.

Acetylgalactosamine↗
PubMed1970

The synthesis of exopolysaccharide by Klebsiella aerogenes membrane preparations and the involvement of lipid intermediates.

1. Membrane preparations from Klebsiella aerogenes type 8 were shown to transfer glucose and galactose from their uridine diphosphate derivatives to a lipid and to polymer. The ratio of glucose to galactose transfer in both cases was 1:2. This is the same ratio in which these sugars occur in native polysaccharide. Galactose transfer was dependent on prior glucosylation of the lipid. Mutants were obtained lacking (a) glucosyltransferase and (b) galactosyltransferase. The transferase activities in a number of non-mucoid mutants was examined. 2. Glucose transfer was partially inhibited by uridine monophosphate, and incorporation of either glucose or galactose into lipid was decreased in the presence of uridine diphosphate. The sugars are thought to be linked to a lipid through a pyrophosphate bond, and treatment of the lipid intermediates with phenol yielded water-soluble compounds. These could be dephosphorylated with alkaline phosphatase. Transfer of glucuronic acid to lipid or polymer from uridine diphosphate glucuronic acid was much lower than that of the other two sugars. 3. The fate of sugars incorporated into polymer was also followed. Some conversion of glucose into galactose and glucuronic acid occurred. Mutants unable to transfer glucose or galactose to lipid were unable to form polymer. Other mutants capable of lipid glycosylation were in some cases unable to form polymer. A model for capsular polysaccharide synthesis is proposed and its similarity to the formation of other polymers outside the cell membrane is discussed.

Alkaline Phosphatase↗
PubMed1970

Control of colanic acid synthesis.

The nucleotide pools of certain mucoid, colanic acid-synthesizing strains of Escherichia coli, Salmonella typhimurium, and Aerobacter cloacae were examined, and in all cases the nucleotide sugars uridine-5'-diphosphate glucose (UDPG), uridine-5'-diphosphate galactose (UDPGal), guanosine-5'-diphosphate fucose (GDPF), and uridine-5'-diphosphate glucuronic acid (UDPGA) were detected. It is postulated that these nucleotide sugars are precursors in the synthesis of colanic acid. The levels of these nucleotide sugars and of the enzymes involved in their synthesis were examined in a number of mucoid strains and compared with the levels found in certain strains which were repressed in the synthesis of colanic acid, only becoming mucoid when grown in the presence of p-fluorophenylalanine (PFA). The levels of UDPG and UDPGal and the enzymes involved in their synthesis were substantially the same in both mucoid and repressed types, but the levels of UDPGA and GDPF and of some of the enzymes involved in their synthesis were much higher in mucoid strains. When repressed strains were grown in the presence of PFA, the levels of UDPGA and GDPF approached those found in mucoid strains. The existence of an operon, containing genes coding for certain key enzymes involved in colanic acid synthesis has been suggested.

Carbon Isotopes↗
PubMed1969

Structural studies on colanic acid, the common exopolysaccharide found in the enterobacteriaceae, by partial acid hydrolysis. Oligosaccharides from colanic acid.

The exopolysaccharide slime colanic acid has been isolated from representative strains of Escherichia coli, Salmonella typhimurium and Aerobacter cloacae. Analysis showed that each polymer contained glucose, galactose, fucose and glucuronic acid, together with acetate and pyruvate. The molar proportions of these components were 1:1.8:1.9:1:1:1 approximately. On the basis of periodate oxidation of the natural and deacetylated polysaccharide, glucose is proposed as the site of the acetyl groups. The pyruvate is attached to galactose. Three neutral oligosaccharides and ten electrophoretically mobile oligosaccharides were isolated and partially characterized. Four of the fragments were esters of pyruvic acid. Most oligosaccharides were isolated from all three polysaccharide preparations. Three further oligosaccharides were isolated from carboxyl-reduced colanic acid and sodium borotritide was used to label the glucose derived from glucuronic acid in these fragments. One trisaccharide was obtained from periodate-oxidized polysaccharide. On the basis of these oligosaccharides a repeating hexasaccharide unit of the following structure is proposed: [Formula: see text] The significance of this structure in colanic acid biosynthesis is discussed.

Acetates↗