2-Dimensional paper chromatography interspersed with reaction on the paper

On the cluster structure of amylopectin

Two opposing models for the amylopectin structure are historically and comprehensively reviewed, which leads us to a better understanding of the specific fine structure of amylopectin. Amylopectin is a highly branched glucan which accounts for approximately 65-85 of starch in most plant tissues. However, its fine structure is still not fully understood due to the limitations of current methodologies. Since the 1940 s, many scientists have attempted to elucidate the distinct structure of amylopectin. One of the most accepted concepts is that amylopectin has a structural element known as "cluster", in which neighboring side chains with a degree of polymerization of ≥ 10 in the region of their non-branched segments form double helices. The double helical structures are arranged in inter- and intra-clusters and are the origin of the distinct physicochemical and crystalline properties of starch granules. Several models of the cluster structure have been proposed by starch scientists worldwide during the progress of analytical methods, whereas no direct evidence so far has been provided. Recently, Bertoft and colleagues proposed a new model designated as "the building block and backbone (BB) model". The BB model sharply contrasts with the cluster model in that the structural element for the BB model is the building block, and that long chains are separately synthesized and positioned from short chains constituting the building block. In the present paper, we conduct the historical review of the cluster concept detailing how and when the concept was established based on experimental results by many scientists. Then, differences between the two opposing concepts are explained and both models are critically discussed, particularly from the point of view of the biochemical regulation of amylopectin biosynthesis.

Contributions of Dexter French (1918-1981) to cycloamylose/cyclodextrin and starch science

Professor Dexter French (1918-1981) was an American chemist and biochemist at Iowa State College (University in 1959). He devoted his career to advance knowledge of polysaccharides and oligosaccharides, in particular starch, cyclodextrins, and enzymes. Cyclodextrins are oligosaccharides obtained from starch and are typically cage molecules with a hydrophobic cavity that can encapsulate other compounds nowadays the basis for many industrial applications. Since the 1960s, he has been recognized as an outstanding authority in the field of starches and cyclodextrins and has inspired researchers in laboratories around the world. This review, on the fortieth anniversary of his death, commemorates his remarkable contribution to starch and cyclodextrin chemistry. Firstly, we give an overview of his personal life and career. Secondly, we highlight some of the results on starch and cyclodextrins from Professor French and his group. A third part discusses his impact on the modern chemistry of cyclodextrins and starch.

Action of Pseudomonas isoamylase on various branched oligo and poly-saccharides

Pseudomonas isoamylase (EC 3.2.1.68) hydrolyzes (1 linked to 6)-alpha-D-glucosidic linkages of amylopectin, glycogen, and various branched dextrins and oligosaccharides. The detailed structural requirements for the substrate are examined qualitatively and quantitatively in this paper, in comparison with the pullulanase of Klebsiella aerogenes. As with pullulanase, Ps. isoamylase is unable to cleave D-glucosyl stubs from branched saccharides. Ps. isoamylase differs from pullulanase in the following characteristics: (1) The favored substrates for Ps. isoamylase are higher-molecular-weight polysaccharides. Most of the branched oligosaccharides examined were hydrolyzed at a lower rate, 10% or less of the rate of hydrolysis of amylopectin. (2) Maltosyl branches are hydrolyzed off by Ps. isoamylase very slowly in comparison with maltotriosyl branches. (3) Ps. isoamylase requires a minimum of three D-glucose residues in the B- or C-chain.

Purification, characterization, and action-pattern studies on the endo-(1 linked to 3)-beta-D-glucanase from Rhizopus arrhizus QM 1032

The extracellular (1 linked to 3)-beta-D-glucanase [(1 linked to 3)-beta-D-glucan glucanohydrolase, EC 3.2.1.6] produced by Rhizopus arrhizus QU 1032 was purified 305-fold in 70% overall yield. This preparation was found to be homogeneous by ultracentrifugation (sedimentation velocity and equilibrium studies), electrophoresis on acrylamide gel with normal, sodium dodecyl sulfate, and urea-acetic acid gels, and upon isoelectric focusing. The amino acid composition of the enzyme has been determined and it possesses a carbohydrate moiety compose of mannose and galactose (in the ratio approximately 5:1) that is linked to the protein through a 2-acetamido-2-deoxyglucose residue. The molecular weight, as determined by equilibrium sedimentation, is 28,800 and this number was confirmed by electrophoresis on gels of sodium dodecyl sulfate. The enzyme does not possess subunit structure. It hydrolyzes its substrates with retention of configuration and possesses transglycosylating ability. The rates of hydrolysis of a wide variety of substrates were determined, and its action pattern on a series of oligosaccharides containing mixed (1 linked to 3)-, (1 linked to 4)-, and (1 linked to 6)-beta-D-glucopyranosyl residues was investigated. The enzyme favors stretches of beta-D-(1 linked to 3) linkages, but it can hydrolyze beta-D-(1 linked to 4) linkages that are flanked on the non-reducing side with stretches of beta-D-(1 linked to 3) links. The enzyme will not act on (1 linked to 6)-beta-D-glucosyl linkages located in stretches of beta-D-(1 linked to 3) and will not act on (1 linked to 3) beta-D-glycosidic linkages involving sugars other than D-glucose.

Enzymes of glycogen mobilization in the photosynthetic procaryote, Anacystis nidulans

Glycogen, the principal storage compound of assimilatory products in Anacystis nidulans, is synthesized in the light and degraded in the dark. (14)C-labelled glycogen and its radioactive limit dextrin obtained by phosphorylase action were used as substrates to identify enzymes involved in glycogen mobilization. A crude homogenate of cells kept in the dark contained the following enzymes: glycogen phosphorylase (EC 2.4.1.1.) that is firmly bound to glycogen, a debranching enzyme that hydrolyzes 1,6-α-glucosidic bonds, and an α-glucosidase (EC 3.2.1.20). Other amylolytic enzymes were not detectable Using ion exchange chromatography on DEAE-cellulose, α-glucosidase and the debranching enzyme could be partly separated from each other and completely from the phosphorylase-glycogen complex. On the basis of their known substrate specificities, the cooperation of these 3 enzymes is sufficient to account for the complete conversion of glycogen into glucose and glucose 1-phosphate.

Purification and some properties of a novel maltohexaose-producing exo-amylase from Aerobacter aerogenes

Maltohexaose producing amylase (EC 3.2.1.-) is the fourth known exo-amylase, the three previously known being glucoamylase, beta-amylase and Pseudomonas stutzeri maltotetraose producing amylase. The enzyme after release from Aerobacter aerogenes cells by 0.1% sodium lauryl sulfate extraction was purified by ammonium sulfate precipitation, DEAE-Sephadex column chromatography and Sephadex G-100 gel filtration to 80-fold of the original sodium lauryl sulfate extract activity, It gave a single band on disc electrophoresis, and the molecular weight by gel filtration was 54 000. This amylase showed maximal activity at 50 degrees C and pH 6.80. The pH stability range was relatively wide, the enzyme retaining more than 90% of its initial activity in the range of 6.50-9.0. 80% of the activity was retained after 15 min at 50 degrees C. This enzyme produced maltohexaose from starch, amylose and amylopectin by exo-attack, but did not act on alpha- or beta-cyclodextrin, pullulan or maltohexaitol. Also the enzyme acted on beta-limit dextrins of amylopectin and glycogen to form branched oligosaccharides. The unusual reaction of this enzyme on beta-limit dextrin is discussed from the standpoint of the stereochemistry of 1,4-alpha- and 1,6-alpha-glucosidic bonds. This is the anomalous amylase for which it is recognized that 1,6-alpha-glucosidic linkages in the substrates can mimic the effect of 1,4-alpha-bonds, as previously observed in pseudo-priming reactions of E. coli phosphorylase.