374
PETER BERNFELD
This property cannot be regarded, however, as a characteristic of the
active protein itself since crystallized amylase from B. subtilis is much
less resistant to temperature and loses its activity at 35° (8). It is more
likely that the crude enzyme contains a stabilizer that is removed during
purification.
The activity of this enzyme, which was found to be an a-amylase
(140, 141), depends on a number of functional groups in the protein.
Thus, —SH and primary —NH 2 appear to be essential for enzyme activity (142), and tyrosyl hydroxyl has been reported to be also necessary
(143), whereas some e-amino groups of lysine only increase the stability
of the enzyme. The influence of the culture medium on the production
of amylase (144) has been studied in detail. Commercial preparations
of B. subtilis amylase are known under the names Rapidase, Superclastase, Biolase, and Liquefase (145). a-Amylases from Biolase and
from a bacterial amylase concentrate from Takamine Laboratory have
been obtained in the crystalline state (146, 147). B. mesentericus amylase is very similar to the enzyme from the culture medium of B. subtilis
(148, 149).
(2). B. polymyxa Amylase. B. polymyxa amylase has been reported
to be much less heat resistant than the B. subtilis enzyme (150). It is
for this reason that Kneen and Beckord classified this enzyme as a separate group. Since the heat resistance of B. subtilis amylase does not
appear to be a property of the enzyme protein itself, but rather an
environmental protective effect, this differentiation between B. subtilis
and B. polymyxa amylases should not be interpreted as an evidence of
differences in their nature, activity, and mechanism of action, in particular since the behavior of these two amylases is otherwise very
similar. B. polymxa amylase develops in a culture medium containing
peptone and starch (151).
(3). Amylase from Clostridium butyricum. Amylase from Clostridium
butyricum has been isolated by Hobson and MacPherson (152) and has
been found to be free of ß-amylase and maltase. The occurrence of this
microorganism in the rumen of the sheep (107) and in the cecum of
the pig (108) may well account for the existence of α-amylase in these
sites.
(4). Amylase from Clostridium acetobutylicum. Amylase from Clostridium acetobutylicum has been found to be associated with considerable amounts of maltase and an «-1,6-glucosidase that hydrolyzes the
branching points of starch (153). Consequently, the end products of
enzymatic action of this mixture are mostly maltose (154).
(5). MisceUaneous bacterial a-amylases. Many other bacteria have
been found to emit α-amylase into the culture medium, e.g., Bacillus
PETER BERNFELD
This property cannot be regarded, however, as a characteristic of the
active protein itself since crystallized amylase from B. subtilis is much
less resistant to temperature and loses its activity at 35° (8). It is more
likely that the crude enzyme contains a stabilizer that is removed during
purification.
The activity of this enzyme, which was found to be an a-amylase
(140, 141), depends on a number of functional groups in the protein.
Thus, —SH and primary —NH 2 appear to be essential for enzyme activity (142), and tyrosyl hydroxyl has been reported to be also necessary
(143), whereas some e-amino groups of lysine only increase the stability
of the enzyme. The influence of the culture medium on the production
of amylase (144) has been studied in detail. Commercial preparations
of B. subtilis amylase are known under the names Rapidase, Superclastase, Biolase, and Liquefase (145). a-Amylases from Biolase and
from a bacterial amylase concentrate from Takamine Laboratory have
been obtained in the crystalline state (146, 147). B. mesentericus amylase is very similar to the enzyme from the culture medium of B. subtilis
(148, 149).
(2). B. polymyxa Amylase. B. polymyxa amylase has been reported
to be much less heat resistant than the B. subtilis enzyme (150). It is
for this reason that Kneen and Beckord classified this enzyme as a separate group. Since the heat resistance of B. subtilis amylase does not
appear to be a property of the enzyme protein itself, but rather an
environmental protective effect, this differentiation between B. subtilis
and B. polymyxa amylases should not be interpreted as an evidence of
differences in their nature, activity, and mechanism of action, in particular since the behavior of these two amylases is otherwise very
similar. B. polymxa amylase develops in a culture medium containing
peptone and starch (151).
(3). Amylase from Clostridium butyricum. Amylase from Clostridium
butyricum has been isolated by Hobson and MacPherson (152) and has
been found to be free of ß-amylase and maltase. The occurrence of this
microorganism in the rumen of the sheep (107) and in the cecum of
the pig (108) may well account for the existence of α-amylase in these
sites.
(4). Amylase from Clostridium acetobutylicum. Amylase from Clostridium acetobutylicum has been found to be associated with considerable amounts of maltase and an «-1,6-glucosidase that hydrolyzes the
branching points of starch (153). Consequently, the end products of
enzymatic action of this mixture are mostly maltose (154).
(5). MisceUaneous bacterial a-amylases. Many other bacteria have
been found to emit α-amylase into the culture medium, e.g., Bacillus