Nitrile hydratase (NHase), an important biotechnological enzyme, has been investigated using a steered molecular dynamics computer modelling for the first time. An external force applied to the docked ligands was used to determine transport paths for acrylonitrile (substrate) and acrylamide (product). The average drag force of 120 pN within the enzyme channel is 50% higher than that in model water. The major hindrance of 500 pN is generated by beta Phe37 residue. This region may be responsible for the stereoselectivity of NHases. (C) 2008 Elsevier B.V. All rights reserved.