TERRAPUB AGri-Bioscience Monographs (AGBM)

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Vol. 7 (No. 2), pp. 25-39, 2017 doi: 10.5047/agbm.2017.00702.0025

Studies on the Chemical Structures of Organic Matrices and Their Functions in the Biomineralization Processes of Molluscan Shells

Michio Suzuki1*, Toshihiro Kogure2 and Hiromichi Nagasawa1

1Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
2Department of Earth and Planetary Science Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
*e-mail: amichiwo@mail.ecc.u-tokyo.ac.jp

(Received on July 12, 2016; Accepted on September 24, 2016; Online published on May 10, 2017)

Abstract: Molluscan shells protect the soft body from predators and the external environment and consist of calcium carbonate in an organic matrix. The interaction between calcium carbonate and the organic matrix forms the microstructure of the molluscan shell. In this review, we discuss several organic molecules that may be important in the formation of the shell microstructure. The iridescent color of pearls is attributed to the characteristic nacreous microstructure of molluscan shells. The Japanese pearl oyster, Pinctada fucata, is used in pearl aquaculture in Japan. The shell of P. fucata consists of two layers, prismatic and nacreous. Prismalin-14 in the prismatic layer interacts with calcium carbonate and binds to chitin. Pif in the nacreous layer interacts with aragonite crystals and plays important roles in forming the organic framework in a compartment-like structure. In contrast, limpets have a crossed lamellar microstructure in their shells. The organic matrices of limpet shells induce the formation of spindle-like aragonite crystals. Recent studies have increased our understanding of the calcification process of molluscan shells, and the findings can be applied to increase yields of high-quality pearls, lowering the cost and energy of pearl aquaculture.

Keywords: aragonite, calcite, crossed lamellar microstructure, Japanese pearl oyster, limpet, nacreous layer, Pinctada fucata, prismatic layer

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