4. ENERGY-RICH COMPOUNDS
131
with metal ions (125, 126), by high viscosity (127), and by their
ability to induce metachromasy (109). The metachromatic reaction
(i.e., the change in color of a dye such as toluidine blue from blue to
pink or purple) has been widely used as a cytological method for
locating polyphosphates in cells.* This method may be quantitated
through the use of spectrophotometric techniques (110, 115-115b).
Polyphosphate-containing granules of bacteria can be detected by
means of electron microscopy (128d, 128e). Highly polymerized polyphosphates can also be determined by measuring the release of Pi, or
by measuring changes in viscosity or sedimentation rate (127) after
acidic or enzymatic hydrolysis (109, 122, 123).
b. Biosynthesis. Pyrophosphate does not appear to be synthesized,
as such, from Pi, but is formed as a by-product from a wide variety of
pyrophosphorylase reactions (50) (cf. Eq. 36). Specific examples include the synthesis of many coenzymes (DPN, CoA, flavin adenine
dinucleotide, cytidine diphosphate choline, uridine diphosphate glucose), of acyl adenylates, of amino acyl adenylates, and of "active Sulfate." Pyrophosphate is also formed by the apyrase-catalyzed hydrolysis
of ATP (129), and from tripolyphosphate as described below (Reaction 38 in reverse).
Tripolyphosphate, trimetaphosphate, and tetrametaphosphate may
appear as intermediates in the degradation of highly polymerized polyphosphate (122, 123, 130). Tripolyphosphate (PPP) may also be synthesized by adenylate kinase via Reaction 38 (131)
PP + ADP ^± PPP + AMP
(38)
or from the splitting of deoxyguanosine triphosphate (and to a lesser
extent guanosine triphosphate) by an enzyme system from Escherichia
coli (131a):
Deoxy-GTP -* Deoxyguanosine + PPP
(38a)
The linear polymer, tetraphosphate, may be synthesized in yeast by
the addition of Pi to cyclic trimetaphosphate (131a).
High molecular weight polyphosphate is rapidly accumulated (113115, 132) when phosphate-starved yeast is placed into a medium containing phosphate. This accumulation is accompanied by the appearance of basophilic or metachromatic granules called "volutin." These
granules were first isolated by Wiame (113, 115), who termed them
"metaphosphate," but subsequent work has shown that this material is,
* Metachromasia results from the polymerization of the dye (128) which may
be induced not only by polyphosphates, but also by glycoproteins (128a) and ribonucleic acid (128b } c), thus indicating that staining properties cannot be used as
the sole criterion for the identification of polyphosphates.
131
with metal ions (125, 126), by high viscosity (127), and by their
ability to induce metachromasy (109). The metachromatic reaction
(i.e., the change in color of a dye such as toluidine blue from blue to
pink or purple) has been widely used as a cytological method for
locating polyphosphates in cells.* This method may be quantitated
through the use of spectrophotometric techniques (110, 115-115b).
Polyphosphate-containing granules of bacteria can be detected by
means of electron microscopy (128d, 128e). Highly polymerized polyphosphates can also be determined by measuring the release of Pi, or
by measuring changes in viscosity or sedimentation rate (127) after
acidic or enzymatic hydrolysis (109, 122, 123).
b. Biosynthesis. Pyrophosphate does not appear to be synthesized,
as such, from Pi, but is formed as a by-product from a wide variety of
pyrophosphorylase reactions (50) (cf. Eq. 36). Specific examples include the synthesis of many coenzymes (DPN, CoA, flavin adenine
dinucleotide, cytidine diphosphate choline, uridine diphosphate glucose), of acyl adenylates, of amino acyl adenylates, and of "active Sulfate." Pyrophosphate is also formed by the apyrase-catalyzed hydrolysis
of ATP (129), and from tripolyphosphate as described below (Reaction 38 in reverse).
Tripolyphosphate, trimetaphosphate, and tetrametaphosphate may
appear as intermediates in the degradation of highly polymerized polyphosphate (122, 123, 130). Tripolyphosphate (PPP) may also be synthesized by adenylate kinase via Reaction 38 (131)
PP + ADP ^± PPP + AMP
(38)
or from the splitting of deoxyguanosine triphosphate (and to a lesser
extent guanosine triphosphate) by an enzyme system from Escherichia
coli (131a):
Deoxy-GTP -* Deoxyguanosine + PPP
(38a)
The linear polymer, tetraphosphate, may be synthesized in yeast by
the addition of Pi to cyclic trimetaphosphate (131a).
High molecular weight polyphosphate is rapidly accumulated (113115, 132) when phosphate-starved yeast is placed into a medium containing phosphate. This accumulation is accompanied by the appearance of basophilic or metachromatic granules called "volutin." These
granules were first isolated by Wiame (113, 115), who termed them
"metaphosphate," but subsequent work has shown that this material is,
* Metachromasia results from the polymerization of the dye (128) which may
be induced not only by polyphosphates, but also by glycoproteins (128a) and ribonucleic acid (128b } c), thus indicating that staining properties cannot be used as
the sole criterion for the identification of polyphosphates.