Linked Life Data

7306510

Source:http://linkedlifedata.com/resource/pubmed/id/7306510

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
21
pubmed:dateCreated
1982-2-12
pubmed:abstractText
The reactivity of the mitochondrial (pI = 5) isoenzyme of horse liver aldehyde dehydrogenase was determined by studying the effects of pH on steady-state velocity, burst magnitude, and molecular weight of the enzyme in the absence and presence of Mg2+ ions. The Mg2+ ion activation of the steady-state velocity at pH 7.5 has been explained through a mechanism involving alteration of the tetrameric enzyme, functioning with half-of-the-sites reactivity, to a dimeric enzyme, functioning with all-of-the-sites reactivity [Takahashi, K., & Weiner, H. (1980) J. Biol. Chem. 255, 8206-8209]. With increasing pH, the tetrameric enzyme dissociated even in the absence of Mg2+ ions to the more active dimeric state. The pH-dependent dissociation was governed by proton release from a group with pK = 9.5. After correcting for the increased number of functioning active sites, determined from the pre-steady-state burst, we calculated that elevated pH also caused an increase in the velocity of the rate-limiting step, hydrolysis of the acyl-enzyme intermediate. This event was governed by the ionization of two groups, with pK = 7.2 and 9.5, respectively. If these groups are directly involved in the catalytic step, a mechanism involving histidine acting as a general base can be proposed for the former group. The latter group may be involved in a charge relay activation process which only occurs at elevated, nonphysiological pH. The importance of the latter is questionable, as there is only a 3-fold increase in Vmax when this group is involved in catalysis.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
13
pubmed:volume
20
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
6225-30
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1981
pubmed:articleTitle
Effects of pH on horse liver aldehyde dehydrogenase: alterations in metal ion activation, number of functioning active sites, and hydrolysis of the acyl intermediate.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.