Kintsu Hiroyuki, Okumura Taiga, Negishi Lumi, Ifuku Shinsuke, Kogure Toshihiro, Sakuda Shohei, Suzuki Michio
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657, Japan.
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 113-0033, Japan.
Biochem Biophys Res Commun. 2017 Jul 22;489(2):89-95. doi: 10.1016/j.bbrc.2017.05.088. Epub 2017 May 17.
Biomineralization, in which organisms create biogenic hard tissues, with hardness or flexibility enhanced by organic-inorganic interaction is an interesting and attractive focus for application of biomimetic functional materials. Calcites in the prismatic layer of Pinctada fucata are tougher than abiotic calcites due to small crystal defects. However, the molecular mechanism of the defect formation remains unclear. Here, chitin and two chitinolytic enzymes, chitinase and chitobiase, were identified as organic matrices related to for the formation of small crystal defects in the prismatic layer. Experiments with a chitinase inhibitor in vivo showed chitinase is necessary to form the prismatic layer. Analysis of calcite crystals, which were synthesized in a chitin hydrogel treated with chitinolytic enzymes, by electron microscopy and X-ray diffraction showed that crystal defects became larger as chitin was more degraded. These results suggest that interactions between chitin and calcium carbonate increase as chitin is thinner.
生物矿化是指生物体形成生物源硬组织，通过有机-无机相互作用增强硬度或柔韧性，这是仿生功能材料应用中一个有趣且有吸引力的研究重点。由于小晶体缺陷，合浦珠母贝棱柱层中的方解石比非生物方解石更坚韧。然而，缺陷形成的分子机制仍不清楚。在这里，几丁质以及两种几丁质分解酶——几丁质酶和壳二糖酶，被确定为与棱柱层中小晶体缺陷形成相关的有机基质。体内使用几丁质酶抑制剂的实验表明，几丁质酶是形成棱柱层所必需的。通过电子显微镜和X射线衍射对在用几丁质分解酶处理的几丁质水凝胶中合成的方解石晶体进行分析，结果表明，随着几丁质降解程度越高，晶体缺陷变得越大。这些结果表明，随着几丁质变薄，几丁质与碳酸钙之间的相互作用增强。
