Isoamylase specificity

The major enzymes that have been used for studying structures of starch polymers and fragments from them are the endo-acting a-amylases, the exo-acting glucoamylase and (3-amylases, and the debranching enzymes, isoamylases and pullulanases. These enzymes have varied and diverse specificities that have been extensively studied (see previous sections). 

Tietz NW, Burlina A, Gerhardt W, Junge W, Malfertheiner P, Murai T, et al. Multicenter evaluation of a specific pancreatic isoamylase assay based on a double monoclonal-antibody technique. Clin Chem 1988 34 2096-102. 

Since treatment of various samples of amylose with yeast isoamylase (see p. 427) caused a significant decrease in specific viscosity and a corresponding increase in / -amylolysis limit, it seems probable that some amylose molecules have a low degree of branching, and that the inter-chain linkages are of the a-D-(l—>6)-glucosidic type, as in amylopectin. However, all samples of amylose do not contain barriers to 3-amylolysis, as shown by the isolation of amylose of molecular weight 2 X 10 and /3-amylolysis limit 95% by dispersion of starch in dimethyl sulfoxide. ... 

The specificity of isoamylase is such that it completely debranches... 

The use of amylose gel cross-linked by epichlorohydrin for affinity chromatography of extracellular isoamylase of Pseudomonas amyloderamosa has been studied. The isoamylase was adsorbed well on the amylose gel and was eluted specifically with maltodextrin. The eluted enzyme was precipitated with ammonium sulphate to remove maltodextrin, and then the solution of the precipitate was dialysed and concentrated by vacuum filtration. By this procedure 96 mg of the enzyme were purified to homogeneity from 20 1 of culture broth in about 70% yield. 

The isoamylase enzyme preparation conforms to the General Specifications and Considerations for Enzyme Preparations Used in Food Processing, prepared by the Committee at its sixty-seventh meeting (Annex 1, reference 184). 

The acute oral toxicity of isoamylase from P. amyloderamosa (no further specifications given) was examined in one study in ddy-N mice (10 per sex per group). This study was also reviewed by the Committee at its fifty-fifth meeting (Annex 1, reference 149). The LDso was >17 g/kg body weight (bw)(Morimotoetal.,... 

The substrate specificities of purified limit dextrinases from ungerminated oats (Avena sativa) and rice Oryza sativd) have been compared with that of a bacterial isoamylase/ The cereal enzymes are able to hydrolyse a-(l 6)-D-glucosidic linkages in oligosaccharides, a-dextrins, pullulan, amylopectin, and the -limit dextrins of amylopectin and glycogen, but are unable to hydrolyse glycogens. 

Pseudomonas amyloderamosa elaborates an isoamylase that specifically hydrolyzes the a-1 -> 6 branch linkages of starch [16-20]. Another enzyme that also will hydrolyze the a-1 6 branch linkages of starch is pullulanase, which is elaborated by a strain of A. aerogenes [20]. This enzyme is a hydrolase that specifically hydrolyzes the a-1 6 linkages of the linear polysaccharide, pullulan... 

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