Linked Life Data

7873597

Source:http://linkedlifedata.com/resource/pubmed/id/7873597

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1995-4-6
pubmed:abstractText
Our previous study on cyclomaltodextrin glucanotransferase (CGTase) by chemical modification implied the importance of one or two histidine residues in the cyclization reaction of the enzyme. Based on a computer modelled three-dimensional structure of the CGTase, five histidine residues were chosen as targets for the site-directed mutagenesis. The histidine residues 98, 140, 233 and 327 were replaced by aspartate and His-177 by proline using polymerase chain reaction-mediated techniques. The CGTase variants H98D, H140D, H233D and H327D resulted in a profound decrease in the cyclizing and amylolytic activities, while mutation H177P had little influence on the activities but affected the thermal stability and the width of the pH optimum. It is suggested that His-98 functions as (or as a significant part of) the subsite 2 for the binding of the substrate in CGTase and therefore H98D destabilizes the intermediate for cyclization, but does not markedly affect the hydrolytic reactions. Mutants H140D and H233D produced only minor amounts of alpha-cyclodextrin, did not exhibit substrate inhibition with maltotriose and showed non-Michaelis-Menten kinetics. It is proposed that the variants H140D, H233D and H327D cause steric hindrances near the active center, while mutation H177D has similar consequences on the same site spatially.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0006-3002
pubmed:author
pubmed:issnType
Print
pubmed:day
22
pubmed:volume
1247
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
97-103
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
The role of histidine residues in the catalytic act of cyclomaltodextrin glucanotransferase from Bacillus circulans var. alkalophilus.
pubmed:affiliation
Department of Biochemistry, University of Turku, Finland.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't