4. ENERGY-RICH COMPOUNDS
163
lating this element in the form of readily available "energy-rich" storage
compounds would have had great selective advantages. Whereas many
of the "energy-rich" compounds are found in all forms of life, there
appears to have been a fundamental dichotomy in the evolution of
plants and animals with respect to storage forms of these compounds.
Higher plants, algae, fungi, and bacteria contain polyphosphates and
certain carboxyl phosphates which may serve as storage compounds:
in animals, this function is performed by the amidine phosphates.
High and low molecular weight inorganic polyphosphates interact
readily with ATP, as discussed earlier. The distribution and even the
chemical characterization of polyphosphates in plants and bacteria have
received little attention and, in fact, the precise role of this class of
compounds in cellular economy is still imperfectly understood. On the
other hand, carboxyl phosphates as energy storage compounds are apparently restricted to bacteria. It is to be hoped that future investigations will supply more detailed information on the distribution of individual polyphosphates or carboxyl phosphates within the classes of
plants and microorganisms. Such data are presently available only for
the amidine phosphates.
The distribution in animals of the "energy-rich" N-phosphate compounds at first appeared to be unambiguous: phosphoarginine was
characteristic of invertebrates, while phosphocreatine was characteristic
of vertebrates. This led, in fact, to the proposal that the animal kingdom be divided into the "creatinate" and "acreatinate" groups (434).
A few invertebrates were found to have both phosphocreatine and
phosphoarginine; these were considered, therefore, to be related to
each other and to vertebrates. More detailed examination of greater
numbers and varieties of animals and the discovery of further N-phosphate compounds revealed that the pattern of distribution of amidine
phosphates is complex. More than one N-phosphate compound has
been found in the following: Porifera, Coelenterata, Annelida, Sipunculoidea, Echinodermata, Hemichordata, and Chordata. Morphological
and embryological comparisons show that although some phyla
(Echinodermata, Hemichordata, and Chordata) having both phosphoarginine and phosphocreatine are related to each other; other phyla
(for example, Annelida and Porifera), also possessing both compounds,
are not closely related. In many phyla, the distribution of phosphoarginine and phosphocreatine may differ between closely related genera,
between species, and even between tissues of a single animal. A number
of animals contain additional IV-phosphate compounds whose distribution cannot be correlated, at the present time, with an accepted evolutionary sequence. Thus, it may be concluded that the type of N-phos-
163
lating this element in the form of readily available "energy-rich" storage
compounds would have had great selective advantages. Whereas many
of the "energy-rich" compounds are found in all forms of life, there
appears to have been a fundamental dichotomy in the evolution of
plants and animals with respect to storage forms of these compounds.
Higher plants, algae, fungi, and bacteria contain polyphosphates and
certain carboxyl phosphates which may serve as storage compounds:
in animals, this function is performed by the amidine phosphates.
High and low molecular weight inorganic polyphosphates interact
readily with ATP, as discussed earlier. The distribution and even the
chemical characterization of polyphosphates in plants and bacteria have
received little attention and, in fact, the precise role of this class of
compounds in cellular economy is still imperfectly understood. On the
other hand, carboxyl phosphates as energy storage compounds are apparently restricted to bacteria. It is to be hoped that future investigations will supply more detailed information on the distribution of individual polyphosphates or carboxyl phosphates within the classes of
plants and microorganisms. Such data are presently available only for
the amidine phosphates.
The distribution in animals of the "energy-rich" N-phosphate compounds at first appeared to be unambiguous: phosphoarginine was
characteristic of invertebrates, while phosphocreatine was characteristic
of vertebrates. This led, in fact, to the proposal that the animal kingdom be divided into the "creatinate" and "acreatinate" groups (434).
A few invertebrates were found to have both phosphocreatine and
phosphoarginine; these were considered, therefore, to be related to
each other and to vertebrates. More detailed examination of greater
numbers and varieties of animals and the discovery of further N-phosphate compounds revealed that the pattern of distribution of amidine
phosphates is complex. More than one N-phosphate compound has
been found in the following: Porifera, Coelenterata, Annelida, Sipunculoidea, Echinodermata, Hemichordata, and Chordata. Morphological
and embryological comparisons show that although some phyla
(Echinodermata, Hemichordata, and Chordata) having both phosphoarginine and phosphocreatine are related to each other; other phyla
(for example, Annelida and Porifera), also possessing both compounds,
are not closely related. In many phyla, the distribution of phosphoarginine and phosphocreatine may differ between closely related genera,
between species, and even between tissues of a single animal. A number
of animals contain additional IV-phosphate compounds whose distribution cannot be correlated, at the present time, with an accepted evolutionary sequence. Thus, it may be concluded that the type of N-phos-