It is hypothesised that the characteristic twin domain structure of serine proteases permits important allosteric responses in the molecule when peptide and protein substrates bind. Such movement would be ideal for stressing the scissile bond in the substrate, thereby making the task of hydrolysis substantially easier. The control of the domain movement can be closely associated with substrate binding, via the N- and C-terminal regions of the enzyme. The hypothesis also suggests that certain inhibitory peptides exert their effect by binding without inducing the domain movement.
