Linked Life Data

11051821

Source:http://linkedlifedata.com/resource/pubmed/id/11051821

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
2000-11-13
pubmed:abstractText
The mutants of Q20L and G247D of glucose isomerase (GI) were constructed by in vitro site-directed mutagenesis of GI gene with double-primersmethod. The recombinant plasmids pTKD-GIQ20L and pTKD-GIG247D were expressed in E. coli K38 strain. The comparison experiments of mutant enzymes with wild-type GI showed that: (1) the optimum temperature of GIQ20L was decreased by 5 degrees C. Its thermostability was only 78% half-time of the wild type. But its substrate affinity was enhanced. (2) The specific-activity of GIG247D was increased by 33%, and the optimum pH was lowered by 0.6 unit. However, the thermostability of GIG247D was decreased. We supposed, based on the above facts and 0.19 nm resolution crystal structure of SM33GI, that Gln20 locates between alpha 0-helix and alpha 1-helix, the substitution of hydrophobic side chain of Leu for hydrophilic side chain of Gln may enhance the hydrophobic interaction of the molecular surface, leading to the decrease of the stability and thermostability of GIQ20L. Gly247 which is the last amino acid of a beta-sheet from 242 to 247 residues locates in the active core of GI. After replacement, Asp247 which has strong negative electricity may change the electrostatic distribution and influence the charge transfer processes of the active core. So the specific-activity of GIG247D was increased. The introduced charge could alter the pKa of dissociable groups and make the optimum pH lower. In addition, the side chain of Asp247 seems to be very crowded in the surrounding space conformation and is easy to exclude with the other side chains, therefore influences the stability of beta-sheet. Furthermore, Asp247 is in the vicinity of the interface of subunits, so it could interfere with the stability of the interaction between subunits. Thus, the GIG247D decreased the thermostability of SM33GI. The higher enzyme activity and the lower optimum pH will be very useful for industrial production of GI.
pubmed:language
chi
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
1000-3061
pubmed:author
pubmed:issnType
Print
pubmed:volume
16
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
469-73
pubmed:dateRevised
2011-11-17
pubmed:meshHeading
pubmed:year
2000
pubmed:articleTitle
[Mutations of Q20L and G247D improved the specific-activity and optimum pH of glucose isomerase].
pubmed:affiliation
Department of Molecular Biology and Cell Biology, School of Life Science, University of Science and Technology of China, Hefei.
pubmed:publicationType
Journal Article, English Abstract, Research Support, Non-U.S. Gov't