Zhang Cen, Xie Liping, Huang Jing, Chen Lei, Zhang Rongqing
Institute of Marine Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.
Biochem Biophys Res Commun. 2006 Apr 7;342(2):632-9. doi: 10.1016/j.bbrc.2006.01.182. Epub 2006 Feb 13.
Tyrosinase (monophenol, L-DOPA: oxygen oxidoreductase, EC 1.14.18.1), a kind of copper-containing phenoloxidase, arouses great interests of scientists for its important role in periostracum formation. A cDNA clone encoding a putative tyrosinase, termed OT47 because of its estimated molecular mass of 47kDa, was isolated from the pearl oyster, Pinctada fucata. This novel tyrosinase shares similarity with the cephalopod tyrosinases and other type 3 copper proteins within two conserved copper-binding sites. RT-PCR analysis showed that OT47 mRNA was expressed only in the mantle edge. Further in situ hybridization analysis and tyrosinase activity staining revealed that OT47 was expressed at the outer epithelial cells of the middle fold, different from early histological results in Mercenaria mercenaria, suggesting a different model of periostracum secretion in P. fucata. Taken together, these results suggest that OT47 is most likely involved in periostracum formation. The identification and characterization of oyster tyrosinase also help to further understand the structural and functional properties of molluscan tyrosinase.
酪氨酸酶（单酚，L - 多巴：氧氧化还原酶，EC 1.14.18.1）是一种含铜的酚氧化酶，因其在贝壳质形成中的重要作用而引起了科学家们的极大兴趣。从合浦珠母贝中分离出一个编码假定酪氨酸酶的cDNA克隆，由于其估计分子量为47kDa，被命名为OT47。这种新型酪氨酸酶在两个保守的铜结合位点与头足类酪氨酸酶和其他3型铜蛋白具有相似性。RT - PCR分析表明，OT47 mRNA仅在套膜边缘表达。进一步的原位杂交分析和酪氨酸酶活性染色显示，OT47在中间褶皱的外上皮细胞中表达，这与硬壳蛤早期的组织学结果不同，表明合浦珠母贝的贝壳质分泌模式不同。综上所述，这些结果表明OT47很可能参与贝壳质的形成。牡蛎酪氨酸酶的鉴定和表征也有助于进一步了解软体动物酪氨酸酶的结构和功能特性。
