Linked Life Data

8384205

Source:http://linkedlifedata.com/resource/pubmed/id/8384205

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
9
pubmed:dateCreated
1993-4-22
pubmed:abstractText
The synthesis of phosphatidylinositol (PI) 4-phosphate and PI 4,5-bisphosphate in the yeast Saccharomyces cerevisiae is stimulated by glucose. PI 4-kinase (ATP:phosphatidylinositol 4-phosphotransferase, EC 2.7.1.67) catalyzes the committed step in the synthesis of these phosphoinositides. Previous studies have suggested that the glucose effect on phosphoinositide synthesis is mediated by cellular levels of ATP and ADP and by the RAS/cAMP pathway. Using purified preparations of the membrane-associated 45- and 55-kDa forms of PI 4-kinase, we examined the regulation of these activities by nucleotides and cAMP-dependent protein kinase. MgADP was a potent inhibitor of both forms of the enzyme. Detailed kinetic analyses of the 45- and 55-kDa enzymes using Triton X-100/PI-mixed micelles showed that MgADP was a competitive inhibitor (Ki = 0.14 and 0.25 mM, respectively) with respect to MgATP and a noncompetitive inhibitor (Ki = 1.3 and 0.9 mM, respectively) with respect to PI. The Ki values for MgADP were about 2-fold lower than the Km values the enzymes have for their substrate MgATP and about 2-fold lower than the cellular concentration of ADP. The 45- and 55-kDa forms of PI 4-kinase activity were regulated differentially by CTP, an important nucleotide involved in phospholipid biosynthesis. Whereas the 55-kDa PI 4-kinase was inhibited by CTP, the 45-kDa enzyme was unaffected by CTP. CTP was a mixed type of inhibitor (Ki = 1.5 mM) with respect to MgATP and a noncompetitive inhibitor (Ki = 4 mM) with respect to PI. The Ki value for CTP was 4-fold higher than the Km value for MgATP and 7-fold higher than the cellular concentration of CTP. The 45- and 55-kDa PI 4-kinases were neither phosphorylated nor regulated by cAMP-dependent protein kinase. These results did not support the previous conclusion that PI 4-phosphate synthesis was mediated by the RAS/cAMP pathway. Our kinetic studies supported the conclusion that the glucose effect on the synthesis of PI 4-phosphate was mediated by cellular levels of ATP and ADP through the regulation of membrane-associated PI 4-kinase activity.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
http://linkedlifedata.com/resource/pubmed/chemical/1-Phosphatidylinositol 4-Kinase, http://linkedlifedata.com/resource/pubmed/chemical/Adenosine Diphosphate, http://linkedlifedata.com/resource/pubmed/chemical/Adenosine Triphosphate, http://linkedlifedata.com/resource/pubmed/chemical/Alkaline Phosphatase, http://linkedlifedata.com/resource/pubmed/chemical/Cytidine Triphosphate, http://linkedlifedata.com/resource/pubmed/chemical/Guanosine Triphosphate, http://linkedlifedata.com/resource/pubmed/chemical/Nucleotides, http://linkedlifedata.com/resource/pubmed/chemical/PIK1 protein, S cerevisiae, http://linkedlifedata.com/resource/pubmed/chemical/Phosphotransferases, http://linkedlifedata.com/resource/pubmed/chemical/Protein Kinases, http://linkedlifedata.com/resource/pubmed/chemical/Saccharomyces cerevisiae Proteins, http://linkedlifedata.com/resource/pubmed/chemical/Uridine Triphosphate
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
268
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
6248-55
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
1993
pubmed:articleTitle
Regulation of the 45- and 55-kDa forms of phosphatidylinositol 4-kinase from the yeast Saccharomyces cerevisiae by nucleotides.
pubmed:affiliation
Department of Food Science, Cook College, Rutgers University, New Brunswick, New Jersey 08903.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't