Detection of endo-acting carbohydrases, particularly in the presence of exoenzymes acting on the smae substrate

Action of glucoamylase from Aspergillus niger on phosphorylated substrate

Glucoamylase (1,4-alpha-D-glucan glucohydrolase, EC 3.2.1.3) from Aspergillus niger was purified to be free from alpha-amylase and phosphatase (glucose 6-phosphate as substrate). The phosphatase was well separated from the glucoamylase by phosphocellulose ion-exchange chromatography. The glucoamylase action was prevented by the esterified phosphate groups of the substrate. Thus, the extensive action of the glucoamylase on potato starch exposed the 6-posphorylglucosyl residue of the starch at the non-reducing terminal and large molecular weight limit dextrins remained. The concomitant action of the phosphatase was necessary for the complete degradation of the starch.

Purification and properties of extracellular xylan hydrolases of Streptomyces exfoliatus

Fractionation of extracellular xylan hydrolases of a strain of Streptomyces exfoliatus MC1 (by salting out, molecular sieving and ion exchange chromatography) revealed the presence of five species of the enzyme. Three major fractions could be purified to homogeneity; two were apparently endohydrolases and the third an exo-xylan hydrolase. The three fractions showed different degrees of affinity to the substrate and differed considerably in their substrate specificities. One of the endo-enzymes was specific to xylan while the other could also attack cellulose, inulin and pectin. The exo-enzyme showed xylanolytic and cellulolytic functions only. The three fractions further differed in their response to the presence of metal ions, mercapto reagents and compounds. Although the pH and temperature optima were different, the three fractions functioned synergistically in the hydrolysis of xylan.

Action of amyloglucosidase on oxidised amylose

The Michaelis constant and maximal velocity of alpha-amylase-free amyloglucosidase decrease with increasing periodate oxidation of amylose. These kinetic features have been explained on the basis of competitive inhibition by the oxidised non-reducing end of the (1 leads to 4)-alpha-D-glucan chain with the active centres of the enzyme. A kinetic model is proposed to demonstrate this special kind of inhibition where the concentration of inhibitor is directly proportional to the substrate concentration. The experimental data fitted this model, and the plots of 1/Km and 1/V against the ratio of oxidised/unoxidised non-reducing end-groups were straight lines.

A new serum alpha-amylase assay of high sensitivity

The use of chemically modified starch substrates for measurement of serum alpha-amylase activity is described. Action of alpha-amylase on such substrates, in the presence of excess fungal glucoamylase, results in the production of glucose in direct proportion to the amount of alpha-amylase present. The glucose produced is measured by a specific enzymic assay. Results obtained by using this new assay correlate well with activities determined by a conventional saccharogenic assay. The new method is of much higher sensitivity, and is less susceptible to interference, than are most other alpha-amylase assay methods.

Variation in average unit chain length of glycogen in relation to developmental stage in Blastocladiella emersonii

Synchronous, single generations of Blastocladiella emersonii were grown along either the ordinary colorless or resistant sporangial plant pathways. Samples of cells were withdrawn at different developmental stages and glycogen was extracted, purified, debranched by isoamylase treatment, and its component unit chains separated by gel permeation chromatography. The elution profiles showed the distribution of unit chains. Average unit chain length was determined for plants at different developmental stages and shown to vary between 9 and 16. Some of these variations were correlated with other developmental events in the fungus.

Patterns of action of glucoamylase isozymes from Aspergillus species on glycogen

Glucoamylase isozymes from black Aspergillus species have been freed of all traces of alpha-amylase by chromatography on Bio-Gel P-100, as evidenced by limited hydrolysis of oxidized amylose. Glucoamylase I retains its ability to hydrolyze rabbit-liver glycogen rapidly. By contrast, glucoamylase II hydrolyzes glycogen slowly, and addition of alpha-amylase to glucoamylase II does not enhance its activity toward glycogen. These results indicate that alpha-amylase is not involved in hydrolysis of glycogen by glucoamylase.

The fine structure of the branched alpha-D-glucan from the blue-green alga Anacystis nidulans: comparison with other bacterial glycogens and phytoglycogen

The fine structure of the glycogen from the blue-green alga Anacystis nidulans has been examined. After selective hydrolysis of all (1 yields 6)-alpha-D linkages by a bacterial isoamylase, the resulting mixture of linear chains was subjected to gel permeation chromatography. For purposes of comparison, the glycogens from Escherichia coli and Arthrobacter sp., amylopectin, phytoglycogen from sweet corn, and shell-fish glycogen were treated similarly. The profiles of the unit chains of A nidulans glycogen and phytoglycogen were closely similar. There was no close resemblance in the size distribution of unit chains for A. nidulans glycogen, other bacterial glycogens, and amylopectin.