Naraoka Tetsushi, Uchisawa Hidemitsu, Mori Haruhide, Matsue Hajime, Chiba Seiya, Kimura Atsuo
Aomori Industrial Research Center, Aomori, Japan.
Eur J Biochem. 2003 Oct;270(19):4026-38. doi: 10.1046/j.1432-1033.2003.03795.x.
Tyrosinase (monophenol, L-DOPA:oxygen oxidoreductase) was isolated from the ink of the squid, Illex argentinus. Squid tyrosinase, termed ST94, was found to occur as a covalently linked homodimeric protein with a molecular mass of 140.2 kDa containing two copper atoms per a subunit. The tyrosinase activity of ST94 was enhanced by proteolysis with trypsin to form a protein, termed ST94t, with a molecular mass of 127.6 kDa. The amino acid sequence of the subunit was deduced from N-terminal amino acid sequencing and cDNA cloning, indicating that the subunit of ST94 is synthesized as a premature protein with 625 amino acid residues and an 18-residue signal sequence region is eliminated to form the mature subunit comprised of 607 amino acid residues with a deduced molecular mass of 68,993 Da. ST94 was revealed to contain two putative copper-binding sites per a subunit, that showed sequence similarities with those of hemocyanins from mollusks, tyrosinases from microorganisms and vertebrates and the hypothetical tyrosinase-related protein of Caenorhabditis elegans. The squid tyrosinase was shown to catalyze the oxidation of monophenols as well as o-diphenols and to exhibit temperature-dependency of o-diphenolase activity like a psychrophilic enzyme.
酪氨酸酶（单酚，L-多巴：氧氧化还原酶）是从阿根廷滑柔鱼的墨汁中分离出来的。鱿鱼酪氨酸酶，称为ST94，被发现是一种共价连接的同二聚体蛋白，分子量为140.2 kDa，每个亚基含有两个铜原子。用胰蛋白酶进行蛋白水解可增强ST94的酪氨酸酶活性，形成一种分子量为127.6 kDa的蛋白，称为ST94t。通过N端氨基酸测序和cDNA克隆推导了亚基的氨基酸序列，表明ST94的亚基作为一种含有625个氨基酸残基的前体蛋白合成，一个18个残基的信号序列区域被去除，形成由607个氨基酸残基组成的成熟亚基，推导分子量为68,993 Da。ST94被发现每个亚基含有两个假定的铜结合位点，这些位点与软体动物血蓝蛋白、微生物和脊椎动物的酪氨酸酶以及秀丽隐杆线虫的假定酪氨酸酶相关蛋白的铜结合位点具有序列相似性。鱿鱼酪氨酸酶被证明可以催化单酚以及邻二酚的氧化，并表现出像嗜冷酶一样的邻二酚酶活性的温度依赖性。
