AMPHIBIAN AND INVERTEBRATE DEVELOPMENT 79
activity of these two enzymes again provides evidence of their different
metabolic roles in the same morphological events.
Von Hahn et ah (1960) studying the caudal tissues of the larva of
Xenopus laevis, confirmed that several glycerophosphates were present.
The addition of various activators gave results which differ from those of
Bellini (1958) on phenylphosphatase in the tail of Bufo vulgaris; whether
this was due to the different substrates or to the different zoological
species used in the experiments, is worthy of further study.
C. Amylases
Amylases are enzymes capable of hydrolysing starch and glycogen,
releasing disaccharides and monosaccharides: the splitting activity of
salivary amylase in the mammals produces maltose and glucose (Pazur
et al., 1950). Depending on the way in which the two components of
starch, amylose and amylopectin, are attacked, one can distinguish an
α-amylase and a ß-amylase; the former is dextrinizing, the latter
saccharifying. Different techniques are used to demonstrate the products of hydrolysis. The action of amylases on starch yields maltose
only, but the presence of glucose indicates that the enzyme maltase is
simultaneously active to complete hydrolysis.
Amylases are present in plants and in all animals, from amoeba to
man; intracellular amylases are probably bound to mitochondria.
Both α-amylases and ß-amylases can be shown to be highly active
in the eggs of Rana esculenta and Bufo vulgaris; the presence of maltase
has also been established by Chromatographie analysis (Urbani and
Scollo Lavizzari, 1955a). Thus an extract of amphibian embryos, reacting on a starch solution, releases from this substrate glucose and maltose
and, possibly, maltotriose and other oligosaccharides. This indicates that
the amphibian embryo, at the earliest stages of development, contains
a group of carbohydrases, which, for lack of more precise identification,
we shall call amylases.
The presence of amylases in amphibian eggs is not a new fact; their
existence from cleavage to hatching of the frog egg was shown by
Herlitzka (1909) and confirmed by Barnes (1939).
The results (Fig. 9) of our studies on ß-amylases (with starch or glycogen as substrate) in the development of Bufo vulgaris (Urbani, 1957)
show two optima of activity at pH 5-8 and 7-8: activity at pH 7-8 is
greatest in the cleaving egg and decreases during development.
Minimum activity is shown shortly before complete yolk resorption,
but activity increases again some considerable time before the beginning
of the larval stage, as in the case of alkaline proteinase.
This remarkable increase can be related to the differentiation of the
gut in the embryo. The first part of the activity curve therefore repre-
activity of these two enzymes again provides evidence of their different
metabolic roles in the same morphological events.
Von Hahn et ah (1960) studying the caudal tissues of the larva of
Xenopus laevis, confirmed that several glycerophosphates were present.
The addition of various activators gave results which differ from those of
Bellini (1958) on phenylphosphatase in the tail of Bufo vulgaris; whether
this was due to the different substrates or to the different zoological
species used in the experiments, is worthy of further study.
C. Amylases
Amylases are enzymes capable of hydrolysing starch and glycogen,
releasing disaccharides and monosaccharides: the splitting activity of
salivary amylase in the mammals produces maltose and glucose (Pazur
et al., 1950). Depending on the way in which the two components of
starch, amylose and amylopectin, are attacked, one can distinguish an
α-amylase and a ß-amylase; the former is dextrinizing, the latter
saccharifying. Different techniques are used to demonstrate the products of hydrolysis. The action of amylases on starch yields maltose
only, but the presence of glucose indicates that the enzyme maltase is
simultaneously active to complete hydrolysis.
Amylases are present in plants and in all animals, from amoeba to
man; intracellular amylases are probably bound to mitochondria.
Both α-amylases and ß-amylases can be shown to be highly active
in the eggs of Rana esculenta and Bufo vulgaris; the presence of maltase
has also been established by Chromatographie analysis (Urbani and
Scollo Lavizzari, 1955a). Thus an extract of amphibian embryos, reacting on a starch solution, releases from this substrate glucose and maltose
and, possibly, maltotriose and other oligosaccharides. This indicates that
the amphibian embryo, at the earliest stages of development, contains
a group of carbohydrases, which, for lack of more precise identification,
we shall call amylases.
The presence of amylases in amphibian eggs is not a new fact; their
existence from cleavage to hatching of the frog egg was shown by
Herlitzka (1909) and confirmed by Barnes (1939).
The results (Fig. 9) of our studies on ß-amylases (with starch or glycogen as substrate) in the development of Bufo vulgaris (Urbani, 1957)
show two optima of activity at pH 5-8 and 7-8: activity at pH 7-8 is
greatest in the cleaving egg and decreases during development.
Minimum activity is shown shortly before complete yolk resorption,
but activity increases again some considerable time before the beginning
of the larval stage, as in the case of alkaline proteinase.
This remarkable increase can be related to the differentiation of the
gut in the embryo. The first part of the activity curve therefore repre-