358
PETER BERNFELD
b. Hydrolytic enzymes which split «-1,4-glucosidic linkages and
liberate glucose either as the sole product of reaction or in conjunction
with dextrins. To this class belong amyloglucosidases and glucamylase.
c. Hydrolytic enzymes which split «-1,6-glucosidic linkages in glycogen and amylopectin. These are amylo-l,6-glucosidase and R-enzyme.
d. Hydrolytic enzymes splitting both «-1,4- and «-1,6-glucosidic
linkages, usually just termed «-glucosidases, or limit dextrinase, and
Clostridium maltase.
e. Enzymes of presumably hydrolytic character, the exact nature of
the linkages split by them being unknown, however, e.g., Z-enzyme (7).
/. Nonhydrolytic enzymes which catalyze both the synthesis and
degradation of the polysaccharides in a reversible manner, such as
phosphorylases and transglucosidases, including Q-enzyme, amylomaltase, and the so-called "amylase" of Bacillus macerans.
Although the enzymes of the latter class are able to bring about the
degradation of starch or glycogen under certain circumstances, they do
not belong to the polysaccharidases since they are not hydrolases, and
they will not be included, therefore, in the present discussion. Names
like amylomaltase, amylosucrase, and, in particular, amylase of B.
macerans may tend to produce confusion between these enzymes and
the true amylases. For this reason, the name of cyclodextrinase had
been suggested earlier for the "amylase" of B. macerans (8). Furthermore, Z-enzyme will not be discussed because of its controversial nature (9) and because of the uncertainty of the chemical nature of the
glucosidic bond it is believed to hydrolyze.
A». «-AMYLASES
1. Changes in the Properties of the Substrate Caused by
Action of Enzyme
Although the picture of the phenomena noticeable during «-amylase
action may be blurred by the presence of other amylolytic enzymes,
the action of pure α-amylase is characterized by the concurrent appearance of the following manifestations, independently of the source from
which the «-amylase was obtained.
a. Increase in Reducing Power of the Substrate. This increase is due
to a decrease in molecular weight of the substrate (amylose, amylopectin or glycogen solutions, or starch paste) resulting in an increase
of both reducing and nonreducing end groups. The reducing power
can be measured by any of the commonly used methods for aldehyde
determinations, e.g., by the copper reagent of Somogyi (10). Since the
reducing sugars in an «-amylatic digest are mixtures of oligosaccharides
PETER BERNFELD
b. Hydrolytic enzymes which split «-1,4-glucosidic linkages and
liberate glucose either as the sole product of reaction or in conjunction
with dextrins. To this class belong amyloglucosidases and glucamylase.
c. Hydrolytic enzymes which split «-1,6-glucosidic linkages in glycogen and amylopectin. These are amylo-l,6-glucosidase and R-enzyme.
d. Hydrolytic enzymes splitting both «-1,4- and «-1,6-glucosidic
linkages, usually just termed «-glucosidases, or limit dextrinase, and
Clostridium maltase.
e. Enzymes of presumably hydrolytic character, the exact nature of
the linkages split by them being unknown, however, e.g., Z-enzyme (7).
/. Nonhydrolytic enzymes which catalyze both the synthesis and
degradation of the polysaccharides in a reversible manner, such as
phosphorylases and transglucosidases, including Q-enzyme, amylomaltase, and the so-called "amylase" of Bacillus macerans.
Although the enzymes of the latter class are able to bring about the
degradation of starch or glycogen under certain circumstances, they do
not belong to the polysaccharidases since they are not hydrolases, and
they will not be included, therefore, in the present discussion. Names
like amylomaltase, amylosucrase, and, in particular, amylase of B.
macerans may tend to produce confusion between these enzymes and
the true amylases. For this reason, the name of cyclodextrinase had
been suggested earlier for the "amylase" of B. macerans (8). Furthermore, Z-enzyme will not be discussed because of its controversial nature (9) and because of the uncertainty of the chemical nature of the
glucosidic bond it is believed to hydrolyze.
A». «-AMYLASES
1. Changes in the Properties of the Substrate Caused by
Action of Enzyme
Although the picture of the phenomena noticeable during «-amylase
action may be blurred by the presence of other amylolytic enzymes,
the action of pure α-amylase is characterized by the concurrent appearance of the following manifestations, independently of the source from
which the «-amylase was obtained.
a. Increase in Reducing Power of the Substrate. This increase is due
to a decrease in molecular weight of the substrate (amylose, amylopectin or glycogen solutions, or starch paste) resulting in an increase
of both reducing and nonreducing end groups. The reducing power
can be measured by any of the commonly used methods for aldehyde
determinations, e.g., by the copper reagent of Somogyi (10). Since the
reducing sugars in an «-amylatic digest are mixtures of oligosaccharides