Composition of Biomineral Organic Matrices with Special Emphasis on Turbot (Psetta maxima) Otolith and Endolymph

Abstract

The soluble organic matrix (OM) of various biominerals (red coral skeleton, oyster shell, sea urchin test, turbot otolith, chicken eggshell) was extracted after demineralization with acetic acid. The protein content of the OM varies strongly from 0.02 to 1.6 microg/mg biomineral whereas proteoglycans present less variations (from 0.7 to 1.4 microg/mg biomineral). Electrophoresis of biominerals OM shows differences in their protein pattern although several bands are present in all matrices. OM of all biominerals shows carbonic anhydrase activity but no activity was detectable in the endolymph. OM of all biominerals also displays an anticalcifying activity. After separation of the OM extracts by chloroform-methanol, 80% of the anticalcifying activity was found in the methanol phase except in the urchin test. After OM precipitation with trichloracetic acid, 70% of the activities was found in the supernatants. Partial biochemical characterization suggests that the anticalcifying factor is a polyanionic and water-soluble molecule, which could be proteoglycans. The endolymph surrounding the otolith also displays an anticalcifying activity although its inhibitous activity was 50 times lower than that of the otolith OM. However, the anticalcifying activity of the endolymph is assumed by a proteic structure (80% activity precipitated with TCA treatment). Our results suggest that both carbonic anhydrase and anticalcifying activities are widespread and play a significant role in the regulation of biomineral formation. Results are discussed in relation to the calcification process that takes place at the fluid-mineral interface.

Nacre Calcification in the Freshwater Mussel Unio pictorum: Carbonic Anhydrase Activity and Purification of a 95 kDa Calcium‐Binding Glycoprotein

“…[36][37][38] One peculiarity of biomineralisation is the occurrence of CA activity in the extracellular skeletal matrix. This has been reported in only a few biological metazoan models: the cnidarian exoskeleton, [39][40] crustacean calcium storage concretions, [41] the fish otolith [42] and the molluscan shell. [9,42] The role of CA in an extracellular calcifying matrix is far from being elucidated.…”

“…This has been reported in only a few biological metazoan models: the cnidarian exoskeleton, [39][40] crustacean calcium storage concretions, [41] the fish otolith [42] and the molluscan shell. [9,42] The role of CA in an extracellular calcifying matrix is far from being elucidated. According to the mainstream hypothesis, CA catalyses the production of bicarbonate ions, which subsequently react with calcium to precipitate calcium carbonate.…”

Otolith matrix proteins OMP-1 and Otolin-1 are necessary for normal otolith growth and their correct anchoring onto the sensory maculae

“…Future analyses of the interaction of these proteins with each other and with calcium carbonate should contribute further insights into the process of biomineralization. In addition, comprehensive studies of other components contained in the otolith, such as minor components of the protein matrix, proteoglycans (Borelli et al, 2003) and polysaccharides (Pisam et al, 2002), as well as of the otolithic membrane and endolymph, will be needed for a precise understanding of the molecular mechanism of otolith formation.…”

An Introduction to Bio‐nanohybrid Materials

“…Besides nacre in pearls and shells, calcium carbonate is also present in sea urchin spines, coral skeleton, eggshell, and the exoskeleton of arthropods, forming organicinorganic hybrid structures by assembly with biomacromolecules (soluble proteins and insoluble matrices) [76][77][78]. Calcite and aragonite are the calcium carbonate polymorphs that constitute the biominerals found in nature, since they show a higher stability than vaterite.…”