A novel laccase (LACB3) from the endophytic fungus, Phomopsis liquidambari, was cloned and its potential to promote peanut growth was evaluated. The full-length cDNA is 1,731 bp, encoding a mature protein of 556 amino acids with a molecular mass of 60.1 kDa. Using 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate), LACB3 exhibited a K (m) and k (cat) of 85 mu M and 92.7 s(-1), respectively. The enzyme had maximal activity at pH 2.5 and 50 A degrees C and retained 50 % of its activity after 20 h at 50 A degrees C. When LACB3 was applied to soil, the peanut biomass was increased by 12 %, and the content of vanillic acid, coumaric acid and 4-hydroxybenzoic acid in soil were decreased by 21, 27 and 40 %, respectively. These results suggest substantial potential for the use of P. liquidambari or its laccase in agriculture.