386
PETER BERNFELD
ley, wheat, rye, and, in lesser amount, oats have been known to contain practically only ß-amylase (197). Traces of α-amylase in ungerminated cereals are thought to originate from the microflora on these
grains (114). According to Kneen et al. (120, 198), the ß-amylase content of cereal grains depends both on variety and on environment of
growth. Thus, a given sample of wheat may have a higher ß-amylase
content than a certain sample of barley, or vice versa; on the average,
however, barley grain tends to have more /?-amylase than wheat grain.
Six-row barley is generally richer in amylase than two-row barley
(199).
The fate of ß-amylase during the processes of ripening and germination has been frequently discussed. The amount of this enzyme in wheat
is believed to increase during the short period of ripening and then to
decrease again because ß-amylase is partially transformed into an inactive "latent" form (115). The latter process appears to be, however,
a mere combination of the enzyme with insoluble proteins, thus rendering ^-amylase less soluble during this stage. During germination, the
activity of /^-amylase of an aqueous extract of barley increases two- to
threefold because of proteolytic liberation of this enzyme from the latent
state, while its total amount does not increase materially (118, 200,
201).
The distribution of ^-amylase within the wheat grain has been
studied by Linderstr0m-Lang et al. (202, 203). No ^-amylase was found
in the aleuron cells, but much in the subaleuronic layer. The amylase
content in the endosperm is fairly low, increasing outward.
Ungerminated grains of corn (maize), millet, sorghum, and rice
and their malts are practically devoid of ß-amylase (117).
(2). Higher plants other than cereals. Rich sources of ß-amylase
occur in ungerminated soybean seeds (204, 205) and in sweet potatoes
(Ipomoea batatas) (206); from the latter source this enzyme has been
obtained in the pure and crystalline state (207). Furthermore, cabbage
has been found to contain amylases of the /?-type (208), and maple
and birch saps have been reported to exhibit ß-amylatic activity associated with a-amylase (133); later reports of the same author stress more
the existence of α-amylase in these sources (132).
h. ß-Amylase in Microorganisms. Certain organisms of B. subtilis,
usually isolated from plant material, are believed to contain /?-amylase
together with α-amylase. Beckord and associates (138, 209) found that
a bacterial isolate, after cultivation on wheat bran moistened with phosphate, developed an amylase different from commercial α-amylase preparations of B. subtilis. Though it dextrinizes starch and, therefore, contains «-amylase, its saccharifying capacity is higher than that of com-
PETER BERNFELD
ley, wheat, rye, and, in lesser amount, oats have been known to contain practically only ß-amylase (197). Traces of α-amylase in ungerminated cereals are thought to originate from the microflora on these
grains (114). According to Kneen et al. (120, 198), the ß-amylase content of cereal grains depends both on variety and on environment of
growth. Thus, a given sample of wheat may have a higher ß-amylase
content than a certain sample of barley, or vice versa; on the average,
however, barley grain tends to have more /?-amylase than wheat grain.
Six-row barley is generally richer in amylase than two-row barley
(199).
The fate of ß-amylase during the processes of ripening and germination has been frequently discussed. The amount of this enzyme in wheat
is believed to increase during the short period of ripening and then to
decrease again because ß-amylase is partially transformed into an inactive "latent" form (115). The latter process appears to be, however,
a mere combination of the enzyme with insoluble proteins, thus rendering ^-amylase less soluble during this stage. During germination, the
activity of /^-amylase of an aqueous extract of barley increases two- to
threefold because of proteolytic liberation of this enzyme from the latent
state, while its total amount does not increase materially (118, 200,
201).
The distribution of ^-amylase within the wheat grain has been
studied by Linderstr0m-Lang et al. (202, 203). No ^-amylase was found
in the aleuron cells, but much in the subaleuronic layer. The amylase
content in the endosperm is fairly low, increasing outward.
Ungerminated grains of corn (maize), millet, sorghum, and rice
and their malts are practically devoid of ß-amylase (117).
(2). Higher plants other than cereals. Rich sources of ß-amylase
occur in ungerminated soybean seeds (204, 205) and in sweet potatoes
(Ipomoea batatas) (206); from the latter source this enzyme has been
obtained in the pure and crystalline state (207). Furthermore, cabbage
has been found to contain amylases of the /?-type (208), and maple
and birch saps have been reported to exhibit ß-amylatic activity associated with a-amylase (133); later reports of the same author stress more
the existence of α-amylase in these sources (132).
h. ß-Amylase in Microorganisms. Certain organisms of B. subtilis,
usually isolated from plant material, are believed to contain /?-amylase
together with α-amylase. Beckord and associates (138, 209) found that
a bacterial isolate, after cultivation on wheat bran moistened with phosphate, developed an amylase different from commercial α-amylase preparations of B. subtilis. Though it dextrinizes starch and, therefore, contains «-amylase, its saccharifying capacity is higher than that of com-