中文摘要：

采用RT-PCR方法，从鲢、鲤、鲫3种鱼类肝脏总RNA中克隆出了谷胱甘肽转移酶Pi型（GSTPi）cDNA序列，推导了其编码的氨基酸序列。3种鱼类GSTPi的ORF全长627bp，编码208个氨基酸。翻译起始密码均为ATG,终止密码子均为TGA。鱼类与哺乳动物、两栖类爪蟾以及节肢动物丝虫之间GSTPi氨基酸序列相似度平均值分别为50％、33％、15％左右。5种鱼类之间的氨基酸序列相似度较大，其中鲤科鱼类之间平均为85％左右。我们以GSTPi为分子标记，用最大简约数法（MP）构建了13个物种的系统进化树，识别出两个大的单系类群：哺乳类组成类群一（bootstrap 100）；鱼类组成类群-（bootstrap 93）。通过比较鱼类与哺乳类GSTPiN末端和c末端功能域的氨基酸组成差异，探讨了淡水鱼类GSTs承担较强的微囊藻毒素去毒能力的可能分子机制。

英文摘要：

Using RT-PCR method, the glutathione transferase Pi cDNAs were cloned from Cyprinus carpio, Hypophthalmichthys molitrix, and Carassius auratus. The open reading frames （ORFs） from the 3 fishes were 627 bp long （encoding for 208 amino acids） with the initial code ATG and the terminal code TGA. The sequence similarity was 50% between fish and mammals, 33% between fish and amphibian, and 15% between fish and arthropoda, respectively. The sequence similarity was big among fishes, and the average value of the 4 cyprinids was about 85%. Phylogenetic tree was constructed for 13 species based on GST Pi amino acid sequences using MP （Maximum Parsimony） method. Two major clusters were recognized： cluster one consisted of Mammals （bootstrap 100） and cluster two consisted of fishes （bootstrap 93）. Based on the sequences analyses of N/C domain of GST Pi, we proposed the detoxification mechanism of freshwater fishes that were thought to have stronger tolerance to microcystins.