11.7 Conclusion
Calcification and decalcification in crustaceans are characteristic in that (1) they
occur synchronously with molting, (2) at least decalcification in the cuticle and
calcification in the stomach are under endocrine control, (3) they occur concurrently in different tissues in an individual, and (4) calcified tissues contain ACC.
A set of calcification and decalcification can be thought as one of various events that
happen during the molting process. Until now, many organic matrices including highmolecular-weight and low-molecular-weight compounds have been identified.
Concerning matrix proteins and peptides in crustacean calcified tissues, most of
them have the R-R consensus sequence responsible for chitin binding. As in other
biominerals, calcium carbonate precipitation in crustaceans occurs on organic scaffold, which is mainly composed of chitin and proteins. So, most matrix proteins and
peptides with chitin-binding ability are produced before calcification and are waiting
for supply of calcium and bicarbonate ions. Most matrix proteins are acidic, and may
concentrate calcium ions leading to the formation of calcium carbonate precipitation.
On the other hand, low-molecular-weight phosphorus compounds recently identified
may be responsible for ACC formation. The role of such low-molecular-weight
compounds has not yet been studied, and will be an important subject in the future.
Another important subject to be solved is how a large amount of calcium and
bicarbonate ions are passed through epithelial cells of exoskeleton and gastrolith
disk, although almost no studies have ever been done.
Acknowledgment A part of this article was supported by a Grant-in-Aid for Creative Basic
Research (17GS0311) from the Ministry of Education, Culture, Sports, Science, and Technology
of Japan.
References
Addadi L, Raz S, Weiner S (2003) Taking advantage of disorder: amorphous calcium carbonate
and its roles in biomineralization. Adv Mater 15:959–970
Aizenberg J, Weiner S, Addadi L (2003) Coexistence of amorphous and crystalline calcium
carbonate in skeletal tissues. Connect Tissue Res 44(Suppl 1):20–25
Andersen SO (1999) Exoskeletal proteins from the crab, Cancer pugrus. Comp Biochem Physiol
A 123:203–211
Andersen SO, Hojrup P, Roepstorff P (1995) Insect cuticular proteins. Insect Biochem Mol Biol
25:411–425
Endo H, Persson P, Watanabe T (2000) Molecular cloning of the crustacean DD4 cDNA encoding
a Ca
2+ -binding protein. Biochem Biophys Res Commun 276:286–291
Faircloth LN, Shafer TH (2007) Differential expression of eight transcripts and their roles in the
cuticle of the blue crab, Callinectes sapidus. Comp Biochem Physiol B 146:370–383
Hampshire F, Horn DHS (1966) Structure of crustecdysone, a crustacean moulting hormone.
Chem Commun (2), 37–38
11 Structure and Function of Matrix Proteins and Peptides
327
Calcification and decalcification in crustaceans are characteristic in that (1) they
occur synchronously with molting, (2) at least decalcification in the cuticle and
calcification in the stomach are under endocrine control, (3) they occur concurrently in different tissues in an individual, and (4) calcified tissues contain ACC.
A set of calcification and decalcification can be thought as one of various events that
happen during the molting process. Until now, many organic matrices including highmolecular-weight and low-molecular-weight compounds have been identified.
Concerning matrix proteins and peptides in crustacean calcified tissues, most of
them have the R-R consensus sequence responsible for chitin binding. As in other
biominerals, calcium carbonate precipitation in crustaceans occurs on organic scaffold, which is mainly composed of chitin and proteins. So, most matrix proteins and
peptides with chitin-binding ability are produced before calcification and are waiting
for supply of calcium and bicarbonate ions. Most matrix proteins are acidic, and may
concentrate calcium ions leading to the formation of calcium carbonate precipitation.
On the other hand, low-molecular-weight phosphorus compounds recently identified
may be responsible for ACC formation. The role of such low-molecular-weight
compounds has not yet been studied, and will be an important subject in the future.
Another important subject to be solved is how a large amount of calcium and
bicarbonate ions are passed through epithelial cells of exoskeleton and gastrolith
disk, although almost no studies have ever been done.
Acknowledgment A part of this article was supported by a Grant-in-Aid for Creative Basic
Research (17GS0311) from the Ministry of Education, Culture, Sports, Science, and Technology
of Japan.
References
Addadi L, Raz S, Weiner S (2003) Taking advantage of disorder: amorphous calcium carbonate
and its roles in biomineralization. Adv Mater 15:959–970
Aizenberg J, Weiner S, Addadi L (2003) Coexistence of amorphous and crystalline calcium
carbonate in skeletal tissues. Connect Tissue Res 44(Suppl 1):20–25
Andersen SO (1999) Exoskeletal proteins from the crab, Cancer pugrus. Comp Biochem Physiol
A 123:203–211
Andersen SO, Hojrup P, Roepstorff P (1995) Insect cuticular proteins. Insect Biochem Mol Biol
25:411–425
Endo H, Persson P, Watanabe T (2000) Molecular cloning of the crustacean DD4 cDNA encoding
a Ca
2+ -binding protein. Biochem Biophys Res Commun 276:286–291
Faircloth LN, Shafer TH (2007) Differential expression of eight transcripts and their roles in the
cuticle of the blue crab, Callinectes sapidus. Comp Biochem Physiol B 146:370–383
Hampshire F, Horn DHS (1966) Structure of crustecdysone, a crustacean moulting hormone.
Chem Commun (2), 37–38
11 Structure and Function of Matrix Proteins and Peptides
327