Effects of some drugs on human erythrocyte 6-phosphogluconate dehydrogenase: an in vitro study

Abstract

The inhibitory effects of some drugs on 6-phosphogluconate dehydrogenase from human erythrocytes have been investigated. For this purpose, initially, erythrocyte 6-phosphogluconate dehydrogenase was purified 3364 times in a yield of 58% by using ammonium sulfate precipitation and 2′,5′-ADP Sepharose 4B affinity gel. A temperature of +4°C was maintained during the purification process. Enzyme activity was determined with the Beutler method by using a spectrophotometer at 340 nm. This method was utilized for all kinetic studies. Many commonly used drugs were investigated in this study. Some drugs (ketotifen (K_i: 8.3 ± 1.7 μM), dacarbazine (K_i: 10.1 ± 0.7 μM), meloxicam (K_i: 50.9 ± 13.2 μM), furosemide (K_i: 127 ± 37.8 μM), methotrexate (K_i: 136.7 ± 25.3 μM), metochloropramide hydrochloride (K_i: 2.1113 ± 0.6979 mM), ritodrine hydrochloride (K_i: 6.0353 ± 1.2783 mM), and gadopentetic acid (K_i: 73.4 ± 21.9 mM)) inhibited enzyme activity in vitro. K_i constants for the enzyme were found by means of Lineweaver–Burk graphs. All drugs showed non-competitive inhibition. In addition, IC₅₀ values of the drugs were determined by plotting activity percent vs [I].

Keywords::

• 6-phosphogluconate dehydrogenase
• erythrocyte
• drug inhibition