Sun Bo-Guang, Chi Heng
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
Int J Biol Macromol. 2016 Jan;82:76-82. doi: 10.1016/j.ijbiomac.2015.10.037. Epub 2015 Oct 30.
Cathepsin S is a member of cysteine cathepsins and belongs to the cathepsin L-like family. In mammals, it is known to participate in various physiological processes and host immune defense. In teleost fish, the function of cathepsin S is less investigated. In the present work, we characterized a cathepsin S homologue (SoCatS) from red drum (Sciaenops ocellatus), a commercially valuable fish in Chinese mariculture. Like all cathepsin S, SoCatS possesses a peptidase domain with four catalytically essential residues (Gln140, Cys146, His285, and Asn305) conserved in the cathepsin S of different organisms. SoCatS shares 60-90% overall sequence identities with known teleost cathepsin S. Phylogenetic profiling indicated that SoCatS is evolutionally close to the cathepsin S of other teleost fish, especially Miichthys miiuy, a member of Sciaenidae family like red drum. SoCatS expression was detected in various tissues and was enhanced by bacterial infection. Purified recombinant SoCatS exhibited apparent peptidase activity with maximum at 50°C and pH 7.5. This activity depended on the catalytic residue Cys146 and was severely reduced by the cathepsin inhibitor E-64. Our results suggest that SoCatS functions as a cysteine protease which is probably involved in the antibacterial immunity of red drum.
组织蛋白酶S是半胱氨酸组织蛋白酶家族的成员，属于组织蛋白酶L样家族。在哺乳动物中，已知它参与各种生理过程和宿主免疫防御。在硬骨鱼中，组织蛋白酶S的功能研究较少。在本研究中，我们鉴定了眼斑拟石首鱼（中国海水养殖中有商业价值的鱼类）中的一种组织蛋白酶S同源物（SoCatS）。与所有组织蛋白酶S一样，SoCatS拥有一个肽酶结构域，其中有四个在不同生物体的组织蛋白酶S中保守的催化必需残基（Gln140、Cys146、His285和Asn305）。SoCatS与已知的硬骨鱼组织蛋白酶S的总体序列同一性为60-90%。系统发育分析表明，SoCatS在进化上与其他硬骨鱼的组织蛋白酶S接近，尤其是与眼斑拟石首鱼同属石首鱼科的鮸鱼。在各种组织中均检测到SoCatS的表达，且细菌感染可增强其表达。纯化的重组SoCatS在50°C和pH 7.5时表现出明显的肽酶活性，且活性最高。该活性依赖于催化残基Cys146，并被组织蛋白酶抑制剂E-64严重降低。我们的结果表明，SoCatS作为一种半胱氨酸蛋白酶发挥作用，可能参与眼斑拟石首鱼的抗菌免疫。
