| pubmed-article:7470479 | rdf:type | pubmed:Citation | lld:pubmed |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C0035820 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C0022023 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C0030346 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C1280500 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C0033727 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C0007382 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C0596801 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C0877853 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C1709450 | lld:lifeskim |
| pubmed-article:7470479 | lifeskim:mentions | umls-concept:C0332120 | lld:lifeskim |
| pubmed-article:7470479 | pubmed:issue | 1 | lld:pubmed |
| pubmed-article:7470479 | pubmed:dateCreated | 1981-5-13 | lld:pubmed |
| pubmed-article:7470479 | pubmed:abstractText | Papain was succinylated in order to increase its solubility above pH 8 so that proton NMR spectroscopy could be used to study the ionization of His-159 at the active site of the enzyme. The pH dependence of NMR spectra of catalytically active succinyl-papain and the methylthio derivative of the active-site cysteinyl residue of succinyl-papain (succinyl-papain-S-SCH3) were determined between pH 6 and 10. The pH dependence of the C epsilon 1 H resonance of His-159 in catalytically active succinyl-papain indicates that His-159 has a pK of about 8.6 in the catalytically active form of the enzyme. The position of this resonance in succinyl-papain-S-SCH3 indicates that when the active-site cysteinyl residue is methylthiolated, His-159 is completely deprotonated between pH 6 and 10. This result is taken as evidence for an imidazolium--thiolate ion-pair interaction between His-159 and Cys-25 wherein neutralization of the charge on the thiolate anion by methylthiolation would be expected to cause a marked decrease in the pK of His-159. A possible catalytic role for the ion pair in the acylation step in papain-catalyzed reactions is proposed wherein attack of a substrate by the imidazolium--thiolate ion pair is accompanied by an increase in the acidity of the imidazolium group that facilitates expulsion of the leaving group of the substrate. | lld:pubmed |
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| pubmed-article:7470479 | pubmed:grant | http://linkedlifedata.com/r... | lld:pubmed |
| pubmed-article:7470479 | pubmed:language | eng | lld:pubmed |
| pubmed-article:7470479 | pubmed:journal | http://linkedlifedata.com/r... | lld:pubmed |
| pubmed-article:7470479 | pubmed:citationSubset | IM | lld:pubmed |
| pubmed-article:7470479 | pubmed:chemical | http://linkedlifedata.com/r... | lld:pubmed |
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| pubmed-article:7470479 | pubmed:status | MEDLINE | lld:pubmed |
| pubmed-article:7470479 | pubmed:month | Jan | lld:pubmed |
| pubmed-article:7470479 | pubmed:issn | 0006-2960 | lld:pubmed |
| pubmed-article:7470479 | pubmed:author | pubmed-author:JohnsonF AFA | lld:pubmed |
| pubmed-article:7470479 | pubmed:author | pubmed-author:ShaferJ AJA | lld:pubmed |
| pubmed-article:7470479 | pubmed:author | pubmed-author:LewisS DSD | lld:pubmed |
| pubmed-article:7470479 | pubmed:issnType | Print | lld:pubmed |
| pubmed-article:7470479 | pubmed:day | 6 | lld:pubmed |
| pubmed-article:7470479 | pubmed:volume | 20 | lld:pubmed |
| pubmed-article:7470479 | pubmed:owner | NLM | lld:pubmed |
| pubmed-article:7470479 | pubmed:authorsComplete | Y | lld:pubmed |
| pubmed-article:7470479 | pubmed:pagination | 48-51 | lld:pubmed |
| pubmed-article:7470479 | pubmed:dateRevised | 2007-11-14 | lld:pubmed |
| pubmed-article:7470479 | pubmed:meshHeading | pubmed-meshheading:7470479-... | lld:pubmed |
| pubmed-article:7470479 | pubmed:meshHeading | pubmed-meshheading:7470479-... | lld:pubmed |
| pubmed-article:7470479 | pubmed:meshHeading | pubmed-meshheading:7470479-... | lld:pubmed |
| pubmed-article:7470479 | pubmed:meshHeading | pubmed-meshheading:7470479-... | lld:pubmed |
| pubmed-article:7470479 | pubmed:meshHeading | pubmed-meshheading:7470479-... | lld:pubmed |
| pubmed-article:7470479 | pubmed:meshHeading | pubmed-meshheading:7470479-... | lld:pubmed |
| pubmed-article:7470479 | pubmed:meshHeading | pubmed-meshheading:7470479-... | lld:pubmed |
| pubmed-article:7470479 | pubmed:year | 1981 | lld:pubmed |
| pubmed-article:7470479 | pubmed:articleTitle | Effect of cysteine-25 on the ionization of histidine-159 in papain as determined by proton nuclear magnetic resonance spectroscopy. Evidence for a his-159--Cys-25 ion pair and its possible role in catalysis. | lld:pubmed |
| pubmed-article:7470479 | pubmed:publicationType | Journal Article | lld:pubmed |
| pubmed-article:7470479 | pubmed:publicationType | Research Support, U.S. Gov't, P.H.S. | lld:pubmed |
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