Carbonic anhydrase was purified and characterized from erythrocytes of the Turkish native chicken, Gerze, for the first time. The enzyme was purified 57.65-fold with a yield of 52%, and a specific activity of 954.08 U/mg proteins having optimum pH at 8.0; optimum temperature at 30 degrees C; optimum ionic strength at 10 mM and stable pH at 8.0. The purified enzyme had apparent K-M and V-max values of 0.73 mM and 0.236 mu mol x min(-1), respectively. Al+3, Hg+2, Cu+2, Pb+2, and Cd+2 showed inhibitory effects on the enzyme. Pb+2 exhibited the strongest inhibitory action. Cd+2 and Hg+2 were moderate inhibitor, whereas Al+3 and Cu+2 showed weaker actions. All tested metals inhibited the enzyme in competitive manner. Our findings indicate that these metals inhibit the chicken enzyme in a similar manner to other alpha-CAs from mammals investigated earlier, but susceptibility to various metals differ between the native chicken and other mammalian enzymes.