Linked Life Data

14747989

Source:http://linkedlifedata.com/resource/pubmed/id/14747989

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2004-1-28
pubmed:abstractText
Human mitochondrial NAD(P)+-dependent malic enzyme was strongly inhibited by Lu3+. The X-ray crystal structures indicated a structural change between the metal-free and Lu3+-containing enzymes (Yang Z, Batra R, Floyd DL, Hung HC, Chang GG, Tong L. Biochem Biophys Res Commun 2000;274:440-444). We characterized the reversible slow-binding mechanism and the structural interconversion between Mn2+- and Lu3+-containing human mitochondrial malic enzymes. When Lu3+ was added, the activity of the human enzyme showed a downward curve over time, similar to that of the pigeon enzyme. The rate of the transformation (k(obs)) from the initial rate to the steady-state rate increased hyperbolically with the concentration of Lu3+, suggesting the involvement of an isomerization step. Lu3+ had a much higher affinity for the isomerized form (K*(i,Lu (app)) = 4.8 microM) than that of the native form (K(i,Lu (app)) = 148 microM). When an excess of Mn2+ was added to the Lu3+-inhibited enzyme, assays of the kinetic activity showed an upward trend, indicating reactivation. This result also indicated that the reactivation was a slow process. Fluorescence quenching experiments confirmed that the Lu3+-induced isomerization was completely reversible. The dynamic quenching constants for the metal-free, Mn2+-containing, and Lu3+-containing enzyme were 3.08, 3.07, and 3.8 M(-1), respectively. When the Lu3+-containing enzyme was treated with excess Mn2+, the dynamic quenching constant returned to the original value (3.09 M(-1)). These results indicated that binding of Mn2+ did not induce any conformational change in the enzyme. The open form transformed to the closed form only after substrate binding. Lu3+, on the other hand, transformed the open form into a catalytically inactive form. Excess Mn2+ could replace Lu3+ in the metal binding site and convert the inactive form back into the open form. This reversible process was slow in both directions because of the same but opposite structural change involved.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
1097-0134
pubmed:author
pubmed:copyrightInfo
Copyright 2004 Wiley-Liss, Inc.
pubmed:issnType
Electronic
pubmed:day
15
pubmed:volume
54
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
404-11
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2004
pubmed:articleTitle
Metal-Induced reversible structural interconversion of human mitochondrial NAD(P)+-dependent malic enzyme.
pubmed:affiliation
Institute of Biochemistry, National Defense Medical Center, Taipei, Taiwan.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't