{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,9]],"date-time":"2025-11-09T07:33:44Z","timestamp":1762673624789},"reference-count":33,"publisher":"Wiley","issue":"2","license":[{"start":{"date-parts":[[2007,5,1]],"date-time":"2007-05-01T00:00:00Z","timestamp":1177977600000},"content-version":"vor","delay-in-days":4809,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["J Eukaryotic Microbiology"],"published-print":{"date-parts":[[1994,3]]},"abstract":"<jats:p><jats:bold>ABSTRACT. <\/jats:bold> The cysteine, cystine, methionine and sulfate uptake and cysteine metabolism of Giardia lamblia was studied. Initial experiments indicated that bathocuproine sulphonate (20 \u03bcM) added to Keister's modified TYI\u2010S\u201033 medium supported the growth of <jats:italic>G. lamblia<\/jats:italic> at low L\u2010cysteine concentration. This allowed the use of high specific activity radiolabeled L\u2010cysteine for further studies. The analyses of L\u2010cysteine uptake by <jats:italic>G. lamblia<\/jats:italic> indicate the presence of at least two different transport systems. The total cysteine uptake was non saturable, with a capacity of 3.7 pmoles per 10<jats:sup>6<\/jats:sup> cells per min per \u03bcM of cysteine, and probably represent passive diffusion. However, cysteine transport was partially inhibited by L\u2010methionine, D\u2010cysteine and DL\u2010homocysteine. indicating that another system specific for SH\u2010containing amino acids is also present. Cysteine uptake was markedly decreased in medium without serum. In contrast to cysteine, the uptake of L\u2010methionine and sulfate were carried out by saiurable systems with apparent K<jats:sub>m<\/jats:sub>, of 71 and 72 \u03bcM, respectively, but the Vmax of the uptake of sulfate was six orders of magnitude lower than the Vmax of methionine uptake. Cystine was not incorporated into trophozoites. [<jats:sup>35<\/jats:sup>S]\u2010labeled L\u2010cysteine and L\u2010methionine, but not [<jats:sup>35<\/jats:sup>S]sulfate, were incorporated into <jats:italic>Giardia<\/jats:italic> proteins, indicating that the parasite lacks the capacity to synthesize cysteine or methionine from sulfate. Neither cystathionine \u03b3 lyase nor crystathionine \u03b3 synthase activities was detected in homogenates of <jats:italic>Giardia lamblia<\/jats:italic>, suggesting that the transsulfuration pathway is not active and there is no conversion of methionine to cysteine. Our data indicate that cysteine is essential for <jats:italic>Giardia<\/jats:italic> because the parasite: a) cannot take up cystine, and b) cannot synthesize cysteine de novo.<\/jats:p>","DOI":"10.1111\/j.1550-7408.1994.tb01491.x","type":"journal-article","created":{"date-parts":[[2007,5,14]],"date-time":"2007-05-14T05:48:02Z","timestamp":1179121682000},"page":"169-175","update-policy":"http:\/\/dx.doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":30,"title":["The Uptake and Metabolism of Cysteine by Giardia lamblia Trophozoites"],"prefix":"10.1111","volume":"41","author":[{"given":"HUGO D.","family":"LUJAN","sequence":"first","affiliation":[]},{"given":"THEODORE E.","family":"NASH","sequence":"additional","affiliation":[]}],"member":"311","published-online":{"date-parts":[[2007,5]]},"reference":[{"key":"e_1_2_1_2_2","doi-asserted-by":"publisher","DOI":"10.1128\/MMBR.55.4.706-732.1991"},{"key":"e_1_2_1_3_2","doi-asserted-by":"publisher","DOI":"10.1016\/0166-6851(89)90127-8"},{"key":"e_1_2_1_4_2","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1093\/genetics\/130.1.51","article-title":"Genetic analysis of a new mutation conferring cysteine auxotrophy in Saccharomyces cerevisiae: updating of the sulfur metabolism pathway,","volume":"130","author":"Cherest H.","year":"1992","journal-title":"Genetics"},{"key":"e_1_2_1_5_2","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.bi.52.070183.001155"},{"key":"e_1_2_1_6_2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.78.12.7492"},{"key":"e_1_2_1_7_2","doi-asserted-by":"publisher","DOI":"10.1016\/0166-6851(92)90224-8"},{"key":"e_1_2_1_8_2","doi-asserted-by":"crossref","first-page":"1719","DOI":"10.1016\/S0021-9258(19)76870-7","article-title":"The reversible binding of half\u2010cystine to serum protein, and its bearing on the cystine requirement of cultured mammalian cells","volume":"235","author":"Eagle H.","year":"1960","journal-title":"J. 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