Abstract
Dopamine-β-hydroxylase catalyzes the β-oxidation of dopamine to noradrenaline while phenylethanolamine-N-methyltransferase converts noradrenaline to adrenaline. Since catecholamine sulfates represent the predominant form of catecholamines in human tissues, we have studied the role of dopamine sulfate and noradrenaline sulfate as alternate substrates for dopamine-β-hydroxylase and phenylethanolamine-N-methyltransferase, respectively. Dopamine 3-sulfate, dopamine 4-sulfate and noradrenaline 3-sulfate were chemically synthesized and exhaustively purified by ion-exchange chromatography. Dopamine-β-hydroxylase and phenylethanolamine-N-methyltransferase were partially purified from human adrenals. Using tyramine as substrate, dopamine-β-hydroxylase is slightly inhibited by dopamine 3-sulfate according to some irreversible or mixed mechanisms. When dopamine-β-hydroxylase was incubated with dopamine 3-sulfate or dopamine 4-sulfate, we were not able to find any synthesis of either noradrenaline sulfate or free noradrenaline. Using phenylethanolamine as substrate, the enzymatic activity of phenylethanolamine-N-methyltransferase remains unchanged with addition of dopamine 3-sulfate, dopamine 4-sulfate or noradrenaline 3-sulfate. It was concluded tha that dopamine sulfate is not an alternate substrate for either dopamine-β-hydroxylase or phenylethanolamine-N-methyltransferase nor is noradrenaline 3-sulfate an alternate substrate for phenylethanolamine-N-methyltransferase.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
