In Vitro Effects of Some Chemotherapeutics on Human Erythrocyte Glucose-6-Phosphate Dehydrogenase Enzyme

In this study; the in vitro effects of some drugs used in chemotherapy on the glucose-6-phosphate dehydrogenase enzyme (G6PD; E.C. 1.1.1.49) purified from human erythrocyte lysate were investigated. In the first stage of the study, G6PD enzyme was purified from human erythrocyte lysate (with a specific activity of 0.243 EU/mg protein, 68.75% yield and 162 purificaion fold) by ammonium sulfate precipitation and 2', 5' Adenosine diphosphate (ADP)-Sepharose 4B gel affinity chromatography. The purity of the enzyme was checked by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In the second stage of the study, the in vitro effects of some chemotherapy drugs such as ibandronic acid, fluorouracil, oxaliplatin, carboplatin, cyclophosphamide, doxorubicin, metoart con and cisplatin on the activity of the purified enzyme were investigated. As a result of the in vitro studies, the drugs ibandronic acid, oxaliplatin and carboplatin, have an inhibitory effect on the enzyme, and IC₅₀ values were calculated as 1.34, 2.05, and 2.43 mM, respectively. In addition, in order to determine the K _i constants and inhibition types for the drugs oxaliplatin and carboplatin, activity measurements were made at five different substrates and three fixed inhibitor concentrations and Lineweaver-Burk graphs were drawn. With the help of these graphs, the K _i constant of oxaliplatin was determined as 19.46 ± 3.38 mM and the K _i constant of carboplatin was 22.37 ± 3.19 mM. It was determined that the inhibition type of both drugs was competitive. It was determined that the drugs fluorouracil, cyclophosphamide, doxorubicin, metoart con, and cisplatin did not have a significant effect on the enzyme activity.