Linked Life Data

1765090

Source:http://linkedlifedata.com/resource/pubmed/id/1765090

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1992-2-14
pubmed:abstractText
Synechococcus glutamate-1-semialdehyde aminotransferase was expressed in large amounts in transformed cells of Escherichia coli. The resulting purified enzyme has an absorption spectrum characteristic of B6-containing enzymes and could be converted to the pyridoxal-phosphate form with excess dioxovalerate (O2Val), and back to the pyridoxamine-phosphate form with diaminovalerate (A2Val). Both enzyme forms are similarly active in the conversion of glutamate 1-semialdehyde (GSA) to 5-aminolevulinate (ALev), suggesting that A2Val and O2Val are intermediates. Initial rates of ALev synthesis at various fixed concentrations of GSA followed typical Michaelis-Menten kinetics (Km of GSA for the pyridoxamine-phosphate form of GSA aminotransferase = 12 microM, kcat = 0.23 s-1). In submicromolar amounts A2Val stimulates ALev synthesis, and in a series of concentrations with various fixed concentrations of GSA, gives a family of parallel lines in Lineweaver-Burk plots (Km for A2Val = 1.0 microM). On the other hand, O2Val gives competitive inhibition of the pyridoxamine-phosphate form of GSA-aminotransferase and mixed-type inhibition of the pyridoxal-phosphate form (Ki for O2Val = 1.4 mM). In general the kinetics were typical of ping-pong bi-bi mechanisms in which A2Val is the second substrate (intermediate) and O2Val is an alternative first substrate. There is no compelling evidence that O2Val accepts an amino group at its C5 position resulting in the direct formation of ALev, or the reverse involving the apparent formation of O2Val from ALev. These results are consistent with the hypothesis that the mechanism of GSA aminotransferase mimics that of other aminotransferases and that A2Val is the intermediate.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
18
pubmed:volume
202
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
749-57
pubmed:dateRevised
2007-7-23
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Characterization of glutamate-1-semialdehyde aminotransferase of Synechococcus. Steady-state kinetic analysis.
pubmed:affiliation
Graduate School of Biochemistry, Brigham Young University, Provo, Utah.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't