Enzyme system for de novo biosynthesis of glycogen in Aerobacter aerogenes

Multiple forms of ADP-glucose-alpha-1,4-glucan alpha-4-glucosyltransferase were obtained from spinach leaves by gradient elution from a DEAE-cellulose column. In the presence of high concentrations of some salts and bovine serum albumin, unprimed activity was found in one (transglucosylase III) of the four fractions eluted from the column. In addition to having unprimed activity, transglucosylase III had a lower K(m) for ADP-glucose, a much higher K(m) for oyster glycogen, greater heat sensitivity and lower affinity for maltose, maltotriose and amylopectin beta-limit dextrin than fractions I, II and IV. In addition, the kinetics at low concentrations of amylose, amylopectin and rabbit liver glycogen were non-linear for transglucosylase III. The properties of transglucosylases I, II and IV were generally similar to each other. Rates of the unprimed reaction at physiological concentrations of ADP-glucose were greater than those found for the primed reaction of fraction III. The product formed by the unprimed reaction was a glucan containing principally alpha-1,4 linkages with some alpha-1,6 linkages. The primer, maltose, at a concentration of 0.5m inhibited the synthesis of the unprimed product.

mentioning

confidence: 99%

Soluble adenosine diphosphate glucose–α-1,4-glucan α-4-glucosyltransferases from spinach leaves

Ozbun

Hawker

Preiss

1972

“…12658, N.C.I.B. 8806) makes this primer function, in principle, possible (Gahan & Conrad, 1968), but we ascribe an action to a-glucosidase (but not pullulanase) similar to that of maltodextrin phosphorylase in E. coli K12 (Schwarz & Hofnung, 1967). Clearly further work with cell-free preparations obtained by a gentler method of cell rupture is necessary.…”

Section: Amylomaltasementioning

confidence: 94%

Pullulanase synthesis in Klebsiella (Aerobacter) aerogenes strains growing in continuous culture

Hope

Dean

1974

1. Pullulanase synthesis was studied in 16 classified (N.C.I.B.) strains and in an industrial strain (R) of Klebsiella aerogenes grown in chemostats containing maltose as inducer and sole carbon source. 2. Maximum synthesis was associated with carbon-limited growth at a low dilution rate (about 0.2h(-1)). The enzyme remained firmly cell-bound and seemed to be located on the cell surface. 3. Three strains had high activity (R, N.C.I.B. 5938, 8017), twelve were intermediate, and two (N.C.I.B. 8153, 9146) had negligible activity but were inducible with pullulan. 4. Pullulan similarly induced low, but adequate, activity in the other strains in conditions (nutrient limitation other than carbon-limitation) in which pullulanase was otherwise very seriously repressed. Nevertheless, in carbon limitation pullulan induced no more enzyme than did maltose, maltotriose or oligosaccharide mixtures, and ;hyperactivity' never developed on protracted culture. 5. Cyclic AMP relieved the transient repression produced by adding glucose to maltose-limited cultures and a further change to glucose-limited conditions led to constitutive pullulanase synthesis. 6. Amylomaltase and alpha-glucosidase activities were also examined but in less detail. 7. The presence of pullulanase in maltose-limited growth is discussed, but no clear function can be assigned to it at present. The molar growth yields for all the strains were very similar, and no correlation was found between the overgrowth of one strain by another and pullulanase activity. Further, any function as a general branching enzyme in polysaccharide synthesis seems unlikely.

“…This was demonstrated for glucose incorporation from UDP-glucose into potato starch (Lavintman & Cardini, 1973;Lavintman et al, 1974) and into glycogen from rat liver (Krisman, 1972(Krisman, , 1973 Krisman Berthiller et al, 1975) and Escherichia coli (Barengo etal., 1975), and for potato starch incorporation from glucose 1-phosphate was also possible (Tandecarz et al, 1975). Analysis of the product after incorporation of radioactive glucose from UDP-glucose by an extract of Aerobacter aerogens suggested that Aerobacter glycogen was also synthesized on a protein primer (Gahan & Conrad, 1968). It has been shown that a slime polysaccharide secreted by the outer root-cap cells of maize was also assembled on a protein.…”

mentioning

confidence: 99%

A protein-glucan intermediate during paramylon synthesis

Tomos¹,

Northcote²

1978

A sodium deoxycholate extract containing glucosyltransferase activity was obtained from a particulate preparation from Euglena gracilis. It transferred glucose from UDP-[14C]glucose into material that was precipitated by trichloroacetic acid. This material released beta-(1 leads to 3)-glucan oligosaccharides into solution on incubation with weak acid, weak alkali and beta-(1 leads to 3)-glucosidase. The products of the incubation of the deoxycholate extract with UDP-[14C]glucose were analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Radioactive bands were obtained that had the properties of beta-(1 leads to 3)-glucan covalently linked to protein by a bond labile to weak acid. High-molecular-weight material containing a beta-(1 leads to 3)-glucan was also shown to be present by gel filtration. The bond linking glucan to aglycone is possibly a pyrophosphate linkage. It is proposed that in Euglena gracilis beta-(1 leads to 3)-glucan (paramylon) is synthesized on a protein primer.