120
P. W. KENT
complete. This indicates at least the possibility of weak chitin arthropodin complexes in which steric interactions and hydrogen bonds may
contribute. Though such complexes may be of biological significance
(172), there is evidence of chemical bonds linking the two macromolecules. Cuticle from puparia (Sarcophaga falculata) and from decalcified
Cancer pagurus can be dissolved in solutions of lithium thiocyanate
and reprecipitated, retaining a chitin-protein complex (105). The existence of a chemically combined chitin-protein complex in the form of
a glycoprotein is indicated in the larval cuticle of Agrianome spinicollis
and elsewhere. Using relatively mild reagents (ethylenediaminetetraacetic acid) to decalcify cuticle of Cancer pagurus, such a glycoprotein
was isolated, containing 5% of peptide constituents (105, 173).
The protein moiety was not removed by the action of such reagents
as Ν,Ν-dimethylformamide or phenol-water, nor by solution and reprecipitation from aqueous lithium thiocyanate. It was presumed therefore to represent a firm chemical linkage.
Using mild methods of isolation (i.e., avoidance of hot alkaline solutions) Hackman (4) has obtained a series of glycoproteins of varying
peptide content (Table II). It is of interest that papain removed
TABLE II
PROTEIN CONTENT OF GLYCOPROTEINS CONTAINING CHITIN
0
Percentage protein
(calc. from nitrogen
Source of glycoprotein
content)
Agrianome spinicollis larval cuticle
6
50
Agrianome spinicollis larval cuticle (papain)
5
Scylla serrata cuticle (EDTA)
15.6
Cancer pagurus cuticle (EDTA)
C
7.5
Cuttlefish shell (EDTA)
51.2
Loligo sp. skeletal pen (lithium thiocyanate)
13.2
a From Hackman (4). (Courtesy Commonwealth Scientific and Industrial Research
Organization, Australia.)
6 Hackman and Goldberg (178).
c Foster and Hackman (105).
protein from larval cuticles of Agrianome spinicollis more efficiently than
did either pepsin or trypsin.
In the six specimens investigated, it can be tentatively concluded
that there is evidence for a covalent chemical bond between chitin and
protein on the following grounds: (a) the methods of isolation minimize
the survival of labile linkages; (b) the protein content can be reduced,
but amino acids still persist in the products even after treatment with
hot alkaline solutions; (c) preparations reisolated after solution in
P. W. KENT
complete. This indicates at least the possibility of weak chitin arthropodin complexes in which steric interactions and hydrogen bonds may
contribute. Though such complexes may be of biological significance
(172), there is evidence of chemical bonds linking the two macromolecules. Cuticle from puparia (Sarcophaga falculata) and from decalcified
Cancer pagurus can be dissolved in solutions of lithium thiocyanate
and reprecipitated, retaining a chitin-protein complex (105). The existence of a chemically combined chitin-protein complex in the form of
a glycoprotein is indicated in the larval cuticle of Agrianome spinicollis
and elsewhere. Using relatively mild reagents (ethylenediaminetetraacetic acid) to decalcify cuticle of Cancer pagurus, such a glycoprotein
was isolated, containing 5% of peptide constituents (105, 173).
The protein moiety was not removed by the action of such reagents
as Ν,Ν-dimethylformamide or phenol-water, nor by solution and reprecipitation from aqueous lithium thiocyanate. It was presumed therefore to represent a firm chemical linkage.
Using mild methods of isolation (i.e., avoidance of hot alkaline solutions) Hackman (4) has obtained a series of glycoproteins of varying
peptide content (Table II). It is of interest that papain removed
TABLE II
PROTEIN CONTENT OF GLYCOPROTEINS CONTAINING CHITIN
0
Percentage protein
(calc. from nitrogen
Source of glycoprotein
content)
Agrianome spinicollis larval cuticle
6
50
Agrianome spinicollis larval cuticle (papain)
5
Scylla serrata cuticle (EDTA)
15.6
Cancer pagurus cuticle (EDTA)
C
7.5
Cuttlefish shell (EDTA)
51.2
Loligo sp. skeletal pen (lithium thiocyanate)
13.2
a From Hackman (4). (Courtesy Commonwealth Scientific and Industrial Research
Organization, Australia.)
6 Hackman and Goldberg (178).
c Foster and Hackman (105).
protein from larval cuticles of Agrianome spinicollis more efficiently than
did either pepsin or trypsin.
In the six specimens investigated, it can be tentatively concluded
that there is evidence for a covalent chemical bond between chitin and
protein on the following grounds: (a) the methods of isolation minimize
the survival of labile linkages; (b) the protein content can be reduced,
but amino acids still persist in the products even after treatment with
hot alkaline solutions; (c) preparations reisolated after solution in