The invention relates to a novel 3D structure encoding a Nocardiopsis protease, as well as to variants of parent protease homologous to Nocardiopsis proteases, preferably of improved thermostability and/or with an amended temperature activity profile. The invention also relates to DNA sequences encoding such variants, their production in a recombinant host cell, as well as methods of using the variants, in particular within the field of animal feed and detergents. The invention furthermore relates to methods of generating and preparing protease variants of amended properties.