So during my studies, I realized that there aren’t many good/clear images of the catecholamine metabolic pathway that are easily searchable via Google images. So, I made my own figure. Everything is adapted from the public domain, but crisped up with some 2020 technology.
The important takeaway here is that tyrosine hydroxylase is the rate limiting step for catecholamine synthesis (see this 1964 article by Nagatsu, et al; PMID: 14216443). Keep in mind the pH optimum for tyrosine hydroxylase was determined to be in around 6, but the experimental procedure that measured radio-labeled metabolites was performed at pH8.5. Interestingly, activity of tyrosine hydroxylase is dependent on the tetrohydrofolate derivative: tetrahydropteridine. So, the rate limiting step of catecholamine synthesis appears to be folate dependent….
A brief pubmed search suggests that no randomized clinical trial has been performed on folate supplementation in shock states. Why are sepsis researchers focusing on “skin vitamins” in the past?