5. ANTIBIOSIS AND ANTIBIOTICS
265
that the antibacterial action of streptomycin might be explained by the
blocking of CoA-SH which is known to play a part in the metabolism
of the two amino acids. This assumption is also in agreement with the
reversal of streptomycin action by pantothenate (51i).
Experiments showing an inhibitory effect of chloramphenicol upon
the lethal action of streptomycin have led to the assumption that it is a
two-stage process. The first phase, chloramphenicol-sensitive, would be
the streptomycin-induced synthesis of a new protein necessary for
bactericidal action (51/).
Neomycin Β is associated with neomycin C in complexes variously
known as neomycins, streptothricin B, fradiomycins, etc., produced by
S. fradiae, S. albogriseus, and Streptomyces spp. (51k). Both contain a
moiety, neomycin A or neamine, which comprises a diaminohexose and
2-deoxystreptamine (see II). In addition to neamine, they yield, upon
degradation, a characteristic disaccharide, neobiosamine Β or C, which
is made up of D-ribose and a specific diaminohexose (neosamine Β or C).
They are therefore also tetrasaccharides. So, finally, is hydroxymycin,
from S. paucisporogenes, which yields pseudo-neamine, itself made up of
2-deoxystreptamine and D-glucosamine, and another disaccharide comprising a pentose and a diaminohexose.
2. Glycosidic Antibiotics
In many other antibiotics, sugars and/or sugar derivatives are associated with an aglycon moiety of greater or lesser importance and of very
variable nature.
For instance, it is a hydroxy fatty acid, saturated in ustilagic acids
(V) from Ustilago zeae and pyolipic acid (VI) from Pseudomonas
pyocyanea, unsaturated in nemotinic acid xyloside (VII) from basidiomycete B-841. In elaiomycin (VIII), from Streptomyces gelaticus, an
amine is linked to methyl-2,4-dideoxy-2-aminotetroside. The aglycon
moiety of homomycin (IX) and of the related or identical hygromycin A
(S. hygroscopicus, S. noboritoensis) is a substituted cinnamic acid. In the
related but simpler hygromycin Β (51l,m), C15H28O10N2, one finds
D-talose (IXb). The related sugar, 6-deoxy-L-talose, was found in the cell
wall of Actinomyces bovis (51n), 6-deoxy-D-talose in a capsular polysaccharide from a gram-negative bacterium (5Ip), and 2-amino-2,6dideoxy-L-talose in pneumosamine
(51q).
Several antibiotics are typical nucleosides. They are supposed to
interfere with synthesis of nucleic acids as a result of their competition
for enzymes with the normal metabolites of which they are structural
analogs (52, 53a). In some of them, adenine is linked to the sugar
moiety: angustose or L-2-ketofucopyranose (X) in angustmycin A (S.
265
that the antibacterial action of streptomycin might be explained by the
blocking of CoA-SH which is known to play a part in the metabolism
of the two amino acids. This assumption is also in agreement with the
reversal of streptomycin action by pantothenate (51i).
Experiments showing an inhibitory effect of chloramphenicol upon
the lethal action of streptomycin have led to the assumption that it is a
two-stage process. The first phase, chloramphenicol-sensitive, would be
the streptomycin-induced synthesis of a new protein necessary for
bactericidal action (51/).
Neomycin Β is associated with neomycin C in complexes variously
known as neomycins, streptothricin B, fradiomycins, etc., produced by
S. fradiae, S. albogriseus, and Streptomyces spp. (51k). Both contain a
moiety, neomycin A or neamine, which comprises a diaminohexose and
2-deoxystreptamine (see II). In addition to neamine, they yield, upon
degradation, a characteristic disaccharide, neobiosamine Β or C, which
is made up of D-ribose and a specific diaminohexose (neosamine Β or C).
They are therefore also tetrasaccharides. So, finally, is hydroxymycin,
from S. paucisporogenes, which yields pseudo-neamine, itself made up of
2-deoxystreptamine and D-glucosamine, and another disaccharide comprising a pentose and a diaminohexose.
2. Glycosidic Antibiotics
In many other antibiotics, sugars and/or sugar derivatives are associated with an aglycon moiety of greater or lesser importance and of very
variable nature.
For instance, it is a hydroxy fatty acid, saturated in ustilagic acids
(V) from Ustilago zeae and pyolipic acid (VI) from Pseudomonas
pyocyanea, unsaturated in nemotinic acid xyloside (VII) from basidiomycete B-841. In elaiomycin (VIII), from Streptomyces gelaticus, an
amine is linked to methyl-2,4-dideoxy-2-aminotetroside. The aglycon
moiety of homomycin (IX) and of the related or identical hygromycin A
(S. hygroscopicus, S. noboritoensis) is a substituted cinnamic acid. In the
related but simpler hygromycin Β (51l,m), C15H28O10N2, one finds
D-talose (IXb). The related sugar, 6-deoxy-L-talose, was found in the cell
wall of Actinomyces bovis (51n), 6-deoxy-D-talose in a capsular polysaccharide from a gram-negative bacterium (5Ip), and 2-amino-2,6dideoxy-L-talose in pneumosamine
(51q).
Several antibiotics are typical nucleosides. They are supposed to
interfere with synthesis of nucleic acids as a result of their competition
for enzymes with the normal metabolites of which they are structural
analogs (52, 53a). In some of them, adenine is linked to the sugar
moiety: angustose or L-2-ketofucopyranose (X) in angustmycin A (S.