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Query: EC:3.1.6.4 (chondroitinase)
 2,039 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A Fisher rat thyroid cell line was maintained in culture and the cells were labeled with [3H]glucosamine, [35S]sulfate, and [35S]cysteine to examine the synthesis of proteoglycans. 3H and 35S radioactivity from these precursors were incorporated into both chondroitin sulfate (CS) and heparan sulfate (HS) proteoglycans. CS proteoglycans were almost exclusively secreted into the medium while HS proteoglycans remained mainly associated with the cell layer. Single chain glycosaminoglycans released by papain digestion or alkaline borohydride treatment of either the CS or HS proteoglycans had average molecular weights of approximately 30,000 on Sepharose CL-6B chromatography. Both CS and HS proteoglycans were relatively small and contained only one or two glycosaminoglycans chains. 3H and 35S incorporation into both CS and HS proteoglycans were increased by thyroid-stimulating hormone (TSH) in a dose-dependent manner, which is in part explained by an adenylate cyclase-dependent mechanism as indicated by a similar effect in response to dibutyryl cAMP. TSH enhanced the incorporation of 35S into CS from [35S]cysteine about 1.5-fold and that from [35S]sulfate about 2-fold. This result demonstrated that the increased 35S incorporation from the [35S]sulfate precursor reflects an actual increase in sulfate incorporation and is not simply a result from an apparent increase in specific activity of the phosphoadenosine phosphosulfate donor. Analysis of disaccharides from chondroitinase digests revealed that the proportion of non-sulfated, 4-sulfated, and 6-sulfated disaccharides was not altered appreciably by TSH. These results, together with the disproportionate increase in 3H incorporation into CS from [3H]glucosamine, indicated that TSH increased the specific activity of the 3H label as well. Chase experiments revealed that CS proteoglycans were rapidly (t1/2 = 15 min) secreted into the medium and that the degradation of cell-associated proteoglycans was enhanced by TSH.
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PMID:Characterization of proteoglycans synthesized by rat thyroid cells in culture and their response to thyroid-stimulating hormone. 312 76

Growth-inhibited mouse mastocytoma P-815 cells at stationary phase contained more histamine, serotonin and adenosine 3',5'-monophosphate (cAMP), and higher activities of histidine decarboxylase and adenylate cyclase than the cells during exponential growth. The elevation of endogenous cAMP levels induced by several growth-inhibiting agents such as N6, O2'-dibutyryl cAMP (Bt2cAMP), prostaglandin E1, AMP and 2-chloroadenosine stimulated several functions characteristic of mastocytoma P-815 cells in culture, elevating the synthesis of histamine and serotonin, the activity of chymotrypsin-like protease, and the incorporation of [35S]sulfate into acidic glycosaminoglycans. 1-Methyl-3-isobutyl-xanthine (MIX), a potent inhibitor of cAMP phosphodiesterase, potentiated stimulatory effect of these agents. The results indicate that cAMP regulates the growth and functions of mastocytoma P-815 cells. [35S]-Sulfated acidic glycosaminoglycans synthesized in cells at stationary phase or in cells treated with Bt2cAMP plus MIX mainly localized in the 3000-10000 x g sedimentable fraction of cell homogenates, and had a molecular weight of 200000 to 400000 based on gel filtration. This acidic glycosaminoglycan was resistant to chondroitinase ABC and the heparin-degrading enzyme present in the 20000 x g sedimentable fraction of the cells, and was identified as a highly sulfated macromolecular heparin based on behaviors on DEAE-cellulose column and on acidic electrophoresis. Cycloheximide suppressed the stimulatory effect of Bt2cAMP on the synthesis of histamine and [35S]-sulfated acidic glycosaminoglycan.
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PMID:Effect of adenosine 3',5'-monophosphate on growth and several functions of cultured mastocytoma P-815 cells. 625 15