ABSTRACT
Objective:In this study,a prokaryotic expression of the 3-ketosteroid-Delta (1)-dehydrogenase (KSDD) which came from Arthrobacter simplex was built.Moreover,in order to investigate the catalytic mechanism of KSDD and improve its stability,the structure of KSDD was predicted by computer and the critical sites were confirmed by site-directed mutations.Methods:The recombinant plasmid was constructed by eukaryotic expression vector pET-22b and the recombinant strain was constructed and expressed in Escherichia coli BL21 (DE3).High-performance liquid chromatography was used to determine the transformation rate of 4-AD to ADD.The KSDD structure and key sites were predicted by SWISS-MODEL.Site-directed mutations for the amino acid residues of key sites were constructed and activities of the mutations were detected.Results:The recombinant strain E.coli pET-22-ksdd was successfully constructed.It was induced to express the dehydrogenase by IPTG and the conversion rate of 4-AD to ADD was 27％ at 21 ℃.The structure of 3-ketosteroid-Delta (1)-dehydrogenase and the four key sites was analyzed by SWISS-MODEL.Four mutants,Y120R,Y320L,Y488F and G492Y were constructed.Mutants Y120R and Y488F were inactivated,so they were proved to be the key active sites of KSDD.The conversion rate of mutant Y320L was consistent with that of wild type,but the stability at 37 ℃ was improved.The conversion rate of mutant G492Y was 1.2 times of the wild type and the stability has been improved at 37 ℃.Conclusions:At present,there are few studies about the structure and catalytic mechanism of dehydrogenase.The active sites of the enzyme were verified by this study,which laid the foundation for the further study of the properties of the enzyme KSDD.
ABSTRACT
BACKGROUND: Recently, some people believed that the mechanisms of primary hepatic carcinoma might be caused by poor differentiation or disdifferentiation of hepatic stem cells. Studies on hepatic stem cells are in the early stage at present, and the theory of "stem cell origins" of human primary hepatic carcinoma deserves further verification. OBJECTIVE: To investigate the activation, distribution, origin and immunological expression characteristics of hepatic stem cells in different histopathologic types of primary hepatic carcinoma. DESIGN: Observational comparative study. SETTING: Tumor Center, Research Institute of Surgery, Daping Hospital, Third Military Medical University of Chinese PLA. PARTICIPANTS: Experiments were performed at the Laboratory of Tumor Center, Research Institute of Surgery, Daping Hospital, Third Military Medical University of Chinese PLA from September 2003 to July 2004. We took 94 cases of hepatic cellular cancer, 12 cases of intrahepatic cholangiocellular carcinoma and 10 cases of mixed hepatocarcinoma paraffin-embedded tissue blocks as research objects, with 5 cases of liver cirrhosis and 4 cases of normal liver as experimental control. These materials were collected from the archive of the Department of Pathology of Daping Hospital. Primary hepatic carcinoma tissues and corresponding adjacent liver tissues were obtained from patients who had undergone surgery for the removal of their tumors. All the patients were not treated by chemotherapy or radiotherapy before the operation. They had signed the informed consent. Main Antibodies were bought from Santa Cruz Company.METHODS: The histological and immunohistochemical characteristics were examined by haematoxylin and eosin staining and immunohistochemistry (SP method), including mouse antihuman cytokeratin 19 monoclonal antibody, mouse antihuman cytokeratin 7 monoclonal antibody, mouse antihuman cytokeratin 8&&18 monoclonal antibody, mouse antihuman c-kit monoclonal antibody, mouse antihuman Thy-1 monoclonal antibody, mouse antihuman alpha fetoprotein monoclonal antibody. MAIN OUTCOME MEASURES: Expression of immunological markers of hepatic stem cells in different histopathologic types. RESULTS: Immunological markers of hepatic stem cells expressed variously in different histopathologic types of primary hepatic carcinoma. Hepatic stem cells differentiated into hepatoma carcinoma cells in all the types. The highest expression rate of hepatic stem cell immunophenotype was found in the mixed hepatocarcinoma (P < 0.05). Immunophenotypes of hepatic stem cells were negative in normal group and cirrhosis group. CONCLUSION: Hepatic stem cells of varied differentiations and origins existed in different histopathologic types of primary hepatic carcinoma.
ABSTRACT
Objective To investigate the activation, distribution, origin, and expression of hepatic stem cells(HSC)in different histological types of primary liver carcinomas. Methods The histological and immunohistochemical features of 94 cases of hepatocellular carcinoma (HCC), 12 cases of intrahepatic cholangiocarcinoma (ICC) and 10 cases of mixed hepatocarcinoma were examined by HE staining and immunohistochemistry SP method, with 5 cases of sclerotic liver and 4 cases of normal liver tissues as control. Results HSC expression was observed and the transfor mation from HSC to carcinoma cell was also noted in the liver. CK7, CK19, c-kit, Thy-1, and AFP were found expressed in different types of hepatic carcinomas and the greatest intensive expression was found in the mixed hepatocarcinoma (P