In vitroinhibitory effects of some heavy metals on human erythrocyte carbonic anhydrases

Abstract

The inhibition of two human carbonic anhydrase (HCA, EC 4.2.1.1) isozymes, the cytosolic HCA I and II, with heavy metal salts of Pb(II), Co(II) and Hg(II)has been investigated. Human erythrocyte CA-I isozyme was purified with a specific activity of 920 EUmg 21 and a yield of 30% and CA-II isozyme was purified with a specific activity of 8000 EUmg 21 and a yield of 40% using Sepharose-4B-L tyrosine-sulfanilamide affinity gel chromatography. The overall purification was approximately 104-fold for HCA-I and 900-fold for HCA-II. The inhibitory effects of different heavy metals (lead, cobalt and mercury) on CA activity were determined at low concentrations using the esterase method under in vitro conditions. K i values for these metals were calculated from Lineweaver-Burk graphs as 1.0, 3.22 and 1.45 mM for HCA-I and 0.059, 1.382 and 0.32 mM for HCA-II respectively. Lead was a noncompetitive inhibitor for HCA-I and competitive for HCA-II, cobalt was competitive for HCA-I and noncompetitive for HCA-II and mercury was uncompetitive for both HCA-I and HCA-II. Lead was the best inhibitor for both HCA-I and HCA-II.

<i>In Vivo</i> Effects of Naringenin and Lead on Rat Erythrocyte Carbonic Anhydrase Enzyme

“…20 Moreover, it is observed that lipid peroxidation products and oxidative stress increased by a considerable amount in the brain tissues of rats administered 500 ppm lead. 12 In addition, researchers have frequently reported the effects of heavy metal ions on different enzymes in previous years and inhibition effect of heavy metals on metabolically imported enzyme such as CA 21 , glucose 6-phopsphate dehydrogenase 22 , cytochrome P450 reductase 23 , glutathione S-transferase 24 have been determined. For example, Ekinci et al 17 and co-workers mentions the inhibition effects of lead, copper, cobalt heavy metals on cytosolic human CA I and II enzyme activities.…”

“…25 Literature shows that many substances like medical drugs, various metals, anions and pesticides have inhibitory effects on CAs. 21,26,27,28 In this study, the effects of lead and naringenin were examined. A comparison of the enzyme activity results of the groups shows that both lead and naringenin inhibit the CA enzyme in erythrocytes.…”

“…For example, Ekinci et al 17 and co-workers mentions the inhibition effects of lead, copper, cobalt heavy metals on cytosolic human CA I and II enzyme activities. 21 Heavy metals have enzyme inhibition property by establishing a bond with the sulfhydryl groups of proteins. 25 Literature shows that many substances like medical drugs, various metals, anions and pesticides have inhibitory effects on CAs.…”

Carbonic Anhydrase and Heavy Metals

“…In humans Ekinci et al (2007) demonstrated the inhibition of two human carbonic anhydrase isozymes in vitro, the cytosolic HCA I and II by lead, cobalt and mercury. Lead was a noncompetitive inhibitor for HCA-I and competitive for HCA-II, cobalt was competitive for HCA-I and noncompetitive for HCA-II and mercury was uncompetitive for both HCA-I and HCA-II.…”

Characterization of carbonic anhydrase from Turkish native “Gerze” chicken and influences of metal ions on enzyme activity

“…The enzyme catalyzes the reversible inter-conversion of carbon dioxide and bicarbonate. This reaction is the main role of CA enzymes in physiological conditions [1][2][3][4][5] . Sixteen isozymes have been described up to now in mammals, the most active ones as catalysts for carbon dioxide hydration being CA II and CA IX 1,2 .…”