Biological systems signal transduction cascades, interaction with

Bioactive peptides usually occur in small quantities and concentrations within complex biological matrices. This is for two reasons firstly, bioactive peptides interact with a cell-surface-bound receptor to convey a message to the cell that is further amplified by second messengers or other signal transduction cascades. Therefore, they are usually produced in low concentrations along with other peptides. Secondly, because the bioactive peptides usually affect carefully balanced biological regulatory systems, their localization and half-life are precisely controlled... 

---