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rdf:type |
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lifeskim:mentions |
umls-concept:C0007382,
umls-concept:C0022634,
umls-concept:C0030346,
umls-concept:C0037791,
umls-concept:C0057751,
umls-concept:C0205145,
umls-concept:C0441712,
umls-concept:C0443286,
umls-concept:C1514873,
umls-concept:C1705241,
umls-concept:C1705242,
umls-concept:C2717970,
umls-concept:C2717971
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pubmed:issue |
2
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pubmed:dateCreated |
1979-4-25
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pubmed:abstractText |
The reactions of papain (EC 3.4.22.2) with substrate-derived diazomethyl ketones reported by Leary, Larsen, Watanabe & Shaw [Biochemistry (1977) 16, 5857--5861] are unusual in that (i) these reagents fail to react with low-molecular-weight thiols and (ii) the rate of reaction with the papain thiol group does not decrease to near-zero values across a pKa of 4 as the pH is decreased. Existing data are shown to suggest an interpretation involving neighbouring-group participation via transient thiohemiketal formation, rate-determining protonation by imidazolium ion and alkylation on sulphur via a three-membered cyclic transition state. Implications for (a) the difference in site-specificity exhibited by halomethyl ketones in their reactions with serine proteinases and cysteine proteinases and (b) stereoelectronic requirements in the mechanism of papain-catalysed hydrolysis are discussed. The possibility of two tetrahedral intermediates between adsorptive complex and acyl-enzyme is indicated.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-11777,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-1225610,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-1249069,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-16743181,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-234862,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-23765,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-23769,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-26335,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-345770,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-4355768,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-4426388,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-4691346,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-4722033,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-5344122,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-5650849,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-5661631,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-5845265,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-588560,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-5916376,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-5980875,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-911797,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-942375,
http://linkedlifedata.com/resource/pubmed/commentcorrection/743223-952885
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
Nov
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pubmed:issn |
0264-6021
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:day |
1
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pubmed:volume |
175
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
761-4
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
pubmed-meshheading:743223-Amino Acid Chloromethyl Ketones,
pubmed-meshheading:743223-Binding Sites,
pubmed-meshheading:743223-Cysteine,
pubmed-meshheading:743223-Diazomethane,
pubmed-meshheading:743223-Endopeptidases,
pubmed-meshheading:743223-Ketones,
pubmed-meshheading:743223-Models, Chemical,
pubmed-meshheading:743223-Molecular Conformation,
pubmed-meshheading:743223-Papain,
pubmed-meshheading:743223-Serine
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pubmed:year |
1978
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pubmed:articleTitle |
Mechanism of the reaction of papain with substrate-derived diazomethyl ketones. Implications for the difference in site specificity of halomethyl ketones for serine proteinases and cysteine proteinases and for stereoelectronic requirements in the papain catalytic mechanism.
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pubmed:publicationType |
Journal Article
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