Microcalorimetric Study on Tyrosine Oxidation Catalyzed by Tyrosinase

Through the method of initial heat release rate, the kinetic property of tyrosine oxidation catalyzed by tyrosinase from Pseudomonas maltophilia was investigated using a LKB-2107 batch microcalorimeter. Tyrosine was catalyzed and oxidized into L-dopa, then into melanin catalyzed by tyrosinase. We found that the tyrosinase reaction obeyed the Michaelis-Menten kinetics, and at 298.15K and pH 7.0, the initial exothermic rate (W0 ) are in the range of 0.1567~0.5704 mJ·s-1, the maximum exothermic rate (Wmax) are in 0.4152 ~ 0.8143mol·L-1, and mean value of the Michaelis constant (Km) is 2.199±0.105104 mol·L-1.

Correlation of ERCC1 and GSTP1 expression in esophageal cancer tissue with platinum-based chemotherapy sensitivity as well as apoptosis and proliferation gene expression

Objective:To study the correlation of ERCC1 and GSTP1 expression in esophageal cancer tissue with platinum-based chemotherapy sensitivity as well as apoptosis and proliferation gene expression.Methods: Patients with advanced esophageal cancer who accepted PF chemotherapy in our hospital between May 2013 and October 2015 were selected, esophageal cancer tissue was collected before the chemotherapy, the patients were divided into chemotherapy sensitivity group and chemotherapy resistance group according to the effect of chemotherapy, and the expression levels of ERCC1, GSTP1 as well as apoptosis and proliferation genes in esophageal cancer tissue were detected.Results:Protein content and positive protein expression rate of ERCC1 and GSTP1 in esophageal cancer tissue of chemotherapy sensitivity group were significantly lower than those of chemotherapy resistance group, MBP1, DEC1 and PTEN protein content were significantly higher than those of chemotherapy resistance group, and PLCE1, CyclinD1 and PAR2 protein content were significantly lower than those of chemotherapy resistance group;MBP1, DEC1 and PTEN protein content in esophageal cancer tissue with positive ERCC1 and GSTP1 expression were significantly lower than those in esophageal cancer tissue with negative ERCC1 and GSTP1 expression while PLCE1, CyclinD1 and PAR2 protein content were significantly higher than those in esophageal cancer tissue with negative ERCC1 and GSTP1 expression.Conclusion:The highly expressed ERCC1 and GSTP1 in esophageal cancer tissue can decreased the cancer cell sensitivity to platinum-based chemotherapeutics, inhibit cell apoptosis and promote cell proliferation during platinum-based chemotherapy.