Myostatin (MSTN) is a potent negative regulator for skeletal muscle growth, and binds to activin type IIB receptor (ActRIIB) for its cellular signal transduction. Administration of the extracellular domain of ActRIIB (ActRIIB-ECD) improved skeletal muscle growth in laboratory animals, suggesting that ActRIIB-ECD can be a useful pharmacological agent to improve skeletal muscle growth of meat-producing animals. In the current study, pig and chicken ActRIIB-ECDs were produced in the Pichia pastoris GS115, and the recombinant proteins were purified from induced culture media by Ni-NTA affinity chromatography. The digestion of pig and chicken ActRIIB-ECDs with PNGase F and glycoprotein staining demonstrated an N-linked glycosylation of these recombinant proteins. Glycoprotein staining also indicated an additional presence of glycosylation in chicken ActRIIB-ECD. Both the pig and chicken ActRIIB-ECDs were shown to inhibit MSTN activity in a reporter gene assay system in vitro. When MSTN-inhibitory potencies were compared by analyzing EC50 values, no difference in MSTN-inhibitory potency was observed between the glycosylated and N-deglycosylated forms of pig or chicken ActRIIB-ECD, suggesting that glycosylation does not affect the bioactivity of ActRIIB-ECD. MSTN-inhibitory potency of chicken ActRIIB-ECD was greater (P < 0.01) than that of pig ActRIIB-ECD. Results of this study demonstrate that bioactive pig and chicken ActRIIB-ECDs can be produced from P. pastoris. In addition, the study indicates that the N-glycosylation status of ActRIIB-ECD does not affect its bioactivity in vitro. (C) 2011 Elsevier Ltd. All rights reserved.