I’m reading on hormones and the book talks about how peptide or amine hormones are easily broken down by proteases present in the blood plasma. This has led me to question the interactions between these proteases and the blood proteins of the blood (such as albumins and globulins). Does having proteases in the blood mean the blood proteins are constantly broken down? How do the blood proteins get anything done then? And what good do binding proteins do in protecting hormones during vascular transit when the binding proteins are also susceptible to blood proteases?
Edit: I’ve been requested to provide some quotes and references.
Because water-soluble hormones can dissolve in blood, many circulate as free hormones, meaning that most of them dissolve directly into the blood and are delivered to their target tissue without binding to a binding protein.
The book goes on to say
Water-soluble hormones, such as proteins, peptides, and amino acid derivatives, have relatively short half-lives because they are rapidly degraded by enzymes, called proteases, within the bloodstream. The kidneys then remove the hormone breakdown products from the blood.
These quotes were from Seeley’s Anatomy and Physiology, 10th edition.