Isomaltose, amylase action

A product manufactured in Japan as Alo mixture (Anomalously Linked Oligosaccharides) contains mainly a range of IMOS (glucose, isomaltose, and panose as principal constituents). It is produced from starch as substrate by the action of alpha-amylase, beta-amylase, and a transglucosidase. It is claimed to have favorable properties for application in the food industry.143... 

The /8-amylase starts from the non-reducing end group and attacks chains with maltose linkages. Only maltose is liberated. Anomalies in the constitution of the chain molecule, such as isomaltose linkages, stop the enzyme action. The length of the chain plays no significant role. Maltotriose and maltose are not attacked. The enzyme is an exo amylase. ... 

Evidence that the n-glucosidic interchain linkages in starch are, in fact, (l->6)-a-n in nature came originally from the isolation of small proportions of 2,3-di-O-methyl-n-glucose after methylation and hydrolysis. This evidence was, however, hardly definitive, as the small amounts of this dimethyl sugar obtained could equally well have arisen as a result of undermethylation or demethylation. The isolation of isomaltose after the action of crude, bacterial alpha-amylase on the polysaccharides is equally equivocal. No pure alpha-amylase is known that gives isomaltose as a product of its action on starch, and it is likely that this product was formed by a contaminating enzyme in the crude preparation of olpho-amylase used. 

It appears that in experiments where good characterization of isomaltose has been achieved, heterogeneous enzyme preparations have been employed, and in experiments where pure enzyme preparations have been used, the isomaltose has been inadequately characterized. In both cases the conclusions concerning the action of amylase tend to be obscure. 

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