Trichbderma reesei is thought to be a promising recombinant host for the production and secretion of complex proteins due to its ability to secrete large amounts of proteins. In this study we identified a functional N-acetyl-beta-glucosaminidase (NAGase) gene Nag1 in T. reesei. Nag1, a putative gene encoding a GH 20 family NAGase in T. reesei, was cloned and homologous overexpressed in the T. reesei RutC30 Delta U3 with a strong cellobiohydrolase1 gene (cbh1) promoter. Nag1 was secreted in its active form and the highest expression level was around 499.85 IU/ml. Nag1 has a molecular mass of 80 kDa. The optimum pH and temperature were 4.0 and 60 degrees C, respectively. (C) 2014 Elsevier Inc. All rights reserved.