Glycosaminoglycans Golgi

Sulfation (or sulfonation) is catalyzed by sulfo-transferases (STs)/ which metabolize phenolS/ hydrox-ylamineS/ or alcohols to sulfate esters as shown in Scheme 11.32/ converting somewhat polar to very polar functionalities that are fully ionized at neutral pH. Like glucuronidatioii/ there are multiple ST subfamilies (more than 10 in humans). One subfamily is cytosolic and associated with drug metabolism and the other is membrane-bound/ localized in the Golgi apparatus/ and associated with sulfation of glycoproteinS/ proteinS/ and glycosaminoglycans (41). The STs are widely distributed in human tissues. Five cytosolic ST isoforms have been identified and characterized in human tissue four catalyze sulfation of phenolS/ one the sulfation of hydroxy steroids. 

Glycosaminoglycan synthesis occurs in the Golgi, which contains enzymes that catalyze the sequential addition of uronate and aminoglycans. Serine hydroxyl groups in the... 

Interestingly, the secretion of FGF family members that mediate tissue repair resembles IL-1 secretion, that is, not involving the Golgi. The FGF family proteins also bind to their receptors by P-barrel structures that interact with a glycan (in this case known to be heparin) during activation. Hyaluronan and heparin are glycosaminoglycans (Sect. 6.3.1). 

It is believed that HA is the earliest evolutional form of glycosaminoglycans. Contrary to HA, other glycosaminoglycans are synthesized in the Golgi apparatus. They covalently bond with proteins to form the proteoglycans, which further transfer into the extracellular matrix by the exocytosis mechanism [41]. Three forms of hyaluronan synthase (HASj, HAS, HAS3) are found in human and vertebrate bodies. The enzyme HAS performs slow synthesis of high molecular weight HA, the enzyme... 

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