ASIAN JOURNAL OF CHEMISTRY ASIAN JOURNAL OF CHEMISTRY https://doi.org/10.14233/ajchem.2017.20484 INTRODUCTION Carbonic anhydrase (CA, EC 4.2.1.1) isozymes are a family of zinc metalloenzymes, which catalyze the inter- conversion of CO2 and HCO3 – [1]. The enzyme discovered about long times years ago [2-4], is abundantly present in mammalian red blood cells and to a lesser extent in different types of tissues and secretory organs [5,6]. In addition, carbonic anhydrase from plant, yeast and bacteria have been reported and partially characterized [5-11]. The important roles of the enzymes in various cell types have been extensively reviewed [5,6]. At present, approximate 14 isozymes (I-XIV) are reported and found to be distributed throughout the living organisms [5,6,11]. The endocrine (or hormonal) system controls many crucial aspects of the working of the body, for example development of sexual characteristics and development of the brain. Hormones generally carry fairly long-lasting messages, in contrast to the rapid signalling of the nervous system. Carbonic anhydrase was a critical enzyme, which can be thought to be affected by hormones, which are widely con- sumed. This in vitro study planned in order to investigate the affect of hormones with or without on the enzyme, which is important with respect to human health. EXPERIMENTAL Purification of carbonic anhydrase from bovine brain tissue: Brain tissue from bovine brain membrane was kept in physiological saline and then washed with 0.09 % NaCl solvent Effects of Some Hormones on Enzyme Activities of Carbonic Anhydrase from Brain in vitro FATMA ERGÜN 1 and NAZAN DEMIR 2,* 1 Ahi Evran University, School of Health Kirsehir, Turkey 2 Department of Chemistry, Faculty of Sciences, Mugla University, 48000 Mugla, Turkey *Corresponding author: Fax: +90 252 2360948; Tel: +90 252 2314439; E-mail: demirn@yahoo.com Received: 29 December 2016; Accepted: 24 March 2017; Published online: 13 May 2017; AJC-18367 Hormones are 3 classes as steroid hormones, peptide and proteohormones and derived hormones from amino acids. The influence of PTH, E2, T3, T4, TSH and cortizole hormones has been investigated on bovine brain carbonic anhydrase in vitro. The effect of each hormone on carbonic anhydrase was investigated by Wilbur-Andersen method modified by Rickly and coworkers. All of the hormones were determined to have inhibition effect, on bovine brain carbonic anhydrase isoenzyme. The I50 values of hormones caused inhibition were determined by means of activity percentage [I] diagrams. The values were PTH, E2, T3, T4, TSH and cortizole were I50: 1.54 × 10 -14 M, 1.72 × 10 -11 M, 3.6 × 10 -8 M, 4.48 × 10 -13 M, 5.73 × 10 -9 M, 1.22 × 10 -11 M for bovine brain carbonic anhydrase, respectively. Keywords: Hormones, Carbonic Anhydrase, Brain, Zn 2+ . Asian Journal of Chemistry; Vol. 29, No. 7 (2017), 1431-1433 until erythrocyte was completely removed from the medium. Carbonic anhydrases isoenzyme from bovine brain was purified by means of affinity column having a structure of Sepharose 4B-L-tyrosine-sulfonyamide [12] and the study was carried out with these enzymes. The elutes were plotted by doing protein determination at 280 nm and CO2-hydratase activity [13] and the purification was controlled with SDS-PAGE [14]. Determination of carbonic anhydrase activity and effect of hormones on isoenzymes: Carbonic anhydrase activity and effect of hormones was assayed by hydration of CO2 was measured by the method of Rickli et al. [13] and Wilbur- Anderson with bromothymol blue as indicator. CO2-Hydratase activity as enzyme unit (EU) was calculated by the equation (to-tc/tc) where to and tc are the times for pH change of the non enzymatic (buffer) and the enzymatic reaction, respectively. Determination of I50 values: The values of I50 (hormone concentration reduced the enzyme activity by 50 %) have been determined graphically using seven different hormone concen- tration. For the hormones shown inhibition effect, the values of I50 with diagram of activity per cent [I] were calculated. RESULTS AND DISCUSSION Many chemicals at relatively low dosage affect the metabolism of biota by altering normal enzyme activity, particularly inhibition of a specific enzyme [15]. The effects can be dramatic and systemic [16]. Indeed, carbonic anhydrase isoenzymes are important enzymes for body metabolism because they regulate pH in most tissue. Therefore, in the