The effect of metal ions on tannase activity was studied. One mM Mg+2 or Hg+ activated tannase activity. Ba+2, Ca+2, Zn+2, Hg+2 and Ag+ inhibited tannase activity at 1.0 mM concentration and Fe+3 and Co+2 completely inhibited tannase activity. Ag+, B+2, Zn+2 and Hg+2 competitively inhibited tannase activity. Among the anions studied I mM Br- or S2O3-2 enhanced tannase activity. Tween 40 and Tween 80 enhanced tannase activity whereas Tween 60 inhibited tannase activity. Sodium lauryl sulfate and Triton X-100 inhibited tannase activity. Urea stimulated tannase activity at a concentration of 1.5 M. Among the chelators chosen for the present study, 1 mM EDTA or 1,10-o-phenanthrolein inhibited tannase activity Dimethyl sulphoxide and beta-mercaptoethanol inhibited tannase activity at I mM concentration whereas soybean extract inhibited tannase activity at concentrations varying from 0.05 to 1.0% (w/v). Among the nitrogen sources selected ammonium ferrous sulfate, ammonium sulfate, ammonium nitrate and ammonium chloride enhanced tannase activity at 0.1% (w/v) concentration. (C) 2002 Elsevier Science Ltd. All rights reserved.