Here we cloned and expressed two alkaline beta-1, 4-endoglucanases of Phaeosphaeria sp. LH21 from deep-sea mud. The two enzymes shared 71 and 63 % of identities with their known beta-1, 4-endoglucanases, respectively. According to the primary and spatial structures, the potential active sites of one of the two enzymes could be Asp122 and Asp11, while the other enzyme could be Asp16. The enzymatic properties of their recombinant enzymes from Pichia pastoris GS115 showed that they were optimally active at pH 8 and 60-65 A degrees C, exhibited > 90 % residual relative activities at pH 3-10, and obtained relative activities > 75 % at pH 5-10.