The presence of a sulfated tyrosine residue was first detected in fibrinopeptide B,'then on fibrinogens, 2 gastrin? and chole~ ystokinin,~ and more recently in several secretory proteins such as immunoglobin G5 and fibronectin! and in an insect neuropeptide designated leuco-~ ulfakinin.~ Presumably, the 0-sulfate ester group is introduced at a posttranslational stage of the biosynthesis but very little is known about the enzyme (s) ...
