I am curious to know whether soluble proteins are active in circulation? or they become active after entering the extracellular space? I know it varies from protein to protein but would like to have an overview on this.
Hi Vivek, what do you mean by "active or inactive"?
Almost all proteinases in the circulation are secreted as zymogens that need to be activated for full function. Same applies to complement, fibrinogen, coagulation factors V and VIII, etc.
Other proteins, e.g. albumin, transferrin, Ig's, etc. are secreted fully functional.