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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 degrees 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 microM), dacarbazine (K(i): 10.1 +/- 0.7 microM), meloxicam (K(i): 50.9 +/- 13.2 microM), furosemide (K(i): 127 +/- 37.8 microM), methotrexate (K(i): 136.7 +/- 25.3 microM), 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, IC(50) values of the drugs were determined by plotting activity percent vs [I].

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Carbonic anhydrases (CAs) play an important function in various physiological and pathological processes. Therefore, many researchers work in this field in order to design and synthesize new drugs. Both inhibitors and activators of CAs, which are associated with the diagnosis and treatment of many diseases, are very important. The emergence of the use of CA activators in the treatment of Alzheimer has led many scholars to work on this issue. In this study, CA activators and inhibitors are determined. The crown ethers compounds (1, 2, 3, 6, 7, 8, and 9) were found to cause activation on enzyme activities of hCA I and II. The AC values on hCA I and II of the compounds are in the range of 4.6565-374.979 μM. The 4 (IC ; 1.301 and 3.215 μM for hCA I and II) and 5 (IC ; 73.96 and 378.5 μM for hCA I and II) compounds were found to cause inhibition on enzyme activities of hCA I and II.

Glucose 6-phosphate dehydrogenase (d-glucose 6-phosphate: NADP(+) oxidoreductase, EC 1.1.1.49; G6PD) is a key enzyme that is localized in all mammal tissues, especially in cytoplasmic sections and that catalyzes the first step of pentose phosphate metabolic pathway. In this study, G6PD enzyme was purified 1444-fold with a yield of 77% from rainbow trout liver using 2',5'-ADP-sepharose-4B affinity chromatography. Moreover, a purity check of the enzyme was performed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Some characteristic features like optimal pH, stable pH, optimal temperature and optimal ionic strength were determined for the purified enzyme. In addition to this, in vitro effects of ions like silver nitrate (Ag(+)), thallium sulphate (TI(+)), cobalt (II) nitrate (Co(2+)) and arsenic (V) oxide (As(5+)) on enzyme activity were researched. Half-maximal inhibitory concentration (IC50) values of Ag(+), Co(2+) and As(5+) metal ions, which showed an inhibitory effect, were found to be 0.0044, 0.084 and 4.058 mM, respectively; and their inhibition constants (K i) were found to be 0.0052 ± 0.00042, 0.087 ± 0.015700 and 4.833 ± 1.753207 mM, respectively. Tl(+) not exhibited inhibitory effect on the enzyme activity.