2. CHITIN AND MUCOSUBSTANCES
117
of label. Roseman (151) has pointed out the anomalous nature of the
apparent reversal of the chitin synthetase of Glaser and Brown (149).
A considerable body of evidence is available on the biochemical steps
in the transformation of D-glucose into D-glucosamine in microorganisms
[reviewed by Roseman (151), Kent (152, 153), Pigman et al. (154)].
The overall scheme for the enzyme stages possibly involved in the synthesis and turnover of chitin can be represented as in Fig. 14.
ATP
Glutamine
D - GlucoseI
D-Glucosamine •
iV-Acetylglucosamine "
Glucose 6-phosphate -
ATP
ATP
Glucosamine
6-phosphate
^Acetyl CoA
Ν - Acety 1-D- glucosamine
6-phosphate
iST-Acetyl-D-glucosamine
1-phosphate
JTP
Chitodextrins- Chitin -
UDP-JV-Acetylglucosamirfe
Primer
FIG. 14. Enzymatic steps in the synthesis and degradation of chitin.
The metabolic fate of N-acetyl-D-glucosamine by enzymatic deacetylation for reentry at the glucose or glucosamine stage is uncertain though a
specific deacetylase has been reported in E. coli (155). In general, however, direct enzymatic regeneration of glucosamine appears to be uncommon or elusive of demonstration.
A chitinase system, in the blood, digestive juices, cuticle, and saliva
of cockroaches, acts on native chitin (95% chitin-5% peptide) yielding
principally N-acetylglucosamine and traces of glucosamine (156). A
similar system was also demonstrated in the termite Coptotermes lacteus.
No evidence could be found for the presence of a deacetylase, however,
117
of label. Roseman (151) has pointed out the anomalous nature of the
apparent reversal of the chitin synthetase of Glaser and Brown (149).
A considerable body of evidence is available on the biochemical steps
in the transformation of D-glucose into D-glucosamine in microorganisms
[reviewed by Roseman (151), Kent (152, 153), Pigman et al. (154)].
The overall scheme for the enzyme stages possibly involved in the synthesis and turnover of chitin can be represented as in Fig. 14.
ATP
Glutamine
D - GlucoseI
D-Glucosamine •
iV-Acetylglucosamine "
Glucose 6-phosphate -
ATP
ATP
Glucosamine
6-phosphate
^Acetyl CoA
Ν - Acety 1-D- glucosamine
6-phosphate
iST-Acetyl-D-glucosamine
1-phosphate
JTP
Chitodextrins- Chitin -
UDP-JV-Acetylglucosamirfe
Primer
FIG. 14. Enzymatic steps in the synthesis and degradation of chitin.
The metabolic fate of N-acetyl-D-glucosamine by enzymatic deacetylation for reentry at the glucose or glucosamine stage is uncertain though a
specific deacetylase has been reported in E. coli (155). In general, however, direct enzymatic regeneration of glucosamine appears to be uncommon or elusive of demonstration.
A chitinase system, in the blood, digestive juices, cuticle, and saliva
of cockroaches, acts on native chitin (95% chitin-5% peptide) yielding
principally N-acetylglucosamine and traces of glucosamine (156). A
similar system was also demonstrated in the termite Coptotermes lacteus.
No evidence could be found for the presence of a deacetylase, however,