Carbohydrase action

S. Kitahata, C. F. Brewer, D. S. Genghof, T. Sawai, and E. J. Hehre, Scope and mechanism of carbohydrase action. Stereocomplementary hydrolytic and glu-cosyl-transferring actions of glucoamylase and glucodextranase with alpha- and beta-D-glucosyl fluoride, J. Biol. Chem., 256 (1981) 6017-6026. 

The difficulties attendant on the isolation of pure enzymes of known specificity is a major barrier to their routine use for the structural analysis of polysaccharides. As the specificities are separated and as the action patterns of carbohydrases become better defined, these enzymes may be expected to play an important and vital role in the investigation of the structure of synthetic polysaccharides containing ordered sequences of sugar residues. Conversely, it may be anticipated that synthetic carbohydrate polymers of known structure will aid in studies of the specificity requirements of purified enzymes. 

Many so-called glycoside hydrolases catalyze some glycosyl transfer to acceptors other than water. However, it has always been assumed that carbohydrases which have strictly or predominantly hydrolytic action on one substrate would necessarily prove solely or predominantly hydrolytic with all utilizable (suitably diluted) substrates. This is the essential assumption of the hydrolase concept it is not made by the glycosylation model, and it is this assumption which our experimental findings, as well as theoretical base, deny. 

We will discuss first whether there is an absolutely definite limit of action for all amylases. In the case of the action of /5-amylase on starch and on a-dextrins this question seems to be settled, but in the case of the malt a-amylase the answer is less certain. But certainly the action of the malt amylase practically stops at a certain limit. There is, however, almost always a very slow further action. It is possible that this slow saccharification of the limit dextrins is due not to the amylases but to other carbohydrases which have no action on starch but which are capable of attacking products with short chains. Under all circumstances it must be kept in mind that when in an experiment the saccharification for practical purposes has stopped and the limit dextrins have been isolated, this does not necessarily mean that the limit dextrins will not be further attacked by the enzyme used. But the velocity of this action is certainly very small compared with the velocity of the action on starch. Thus, it must be admitted that experiments involving the isolation of the limit dextrins after the action of a certain amylase on starch are in most cases not strictly reproducible. TJie total yield and chain length distribution of limit dextrins may vary, but their general character is not affected. If a limit dextrin produced by a certain amylase is treated with the same enzyme for a very long time, it is very often transformed to another limit dextrin of lower molecular weight with concomi-... 

In D. punctata an endogenous AST also had a stimulating action using ligatured midgets in vitro it was found that this AST stimulated the activity of the carbohydrases, amylase and invertase. 

Heparins and heparinoids form complexes with proteins and bases, and as shown by the ability to produce metachromasia with submicro quantities are very effective complexing agents in trace amounts. Hence, these substances in trace amounts affect many biological agents such as enzymes, etc. When heparin or a heparinoid is injected in animal or man, an enzyme appears in the blood plasma, lipoprotein lipase. When an oil emulsion is incubated with varying amounts of blood plasma obtained after injection of heparin, the oil is cleared. The heparin has caused the release of this enzyme from tissues to the blood. Heparin and heparinoids have a pronounced action on many enzymes - proteolytic enzymes, carbohydrases, etc. and may inhibit, activate. 

McManus 68) found that pretreatment of tissue sections with crude fungal pectinase prevented the coloration of various tissue carbohydrates by the periodic acid - Schiff reaction. Prior acetylation of tissue sections prevented this effect of pectinase. Blockage of pectinase action by acetylation was reversible if saponification was performed before the enzyme treatment. There will undoubtedly be wider histochemical use of pectinases and the many other carbohydrases (see Chapters X and XII) as purer preparations and further knowledge of their indications and limitations are obtained. 

Treimo, J., Westereng, B., Horn, S.J. et al. (2009) Enzymatic solubilization of brewers spent grain by combined action of carbohydrases and peptidases. J. Agric. Food Chem., 57, 3316-3324. 

---