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Several natural and unnatural inositol phosphates and analogues
were analyzed for their ability to inhibit the in vitro phosphatidylinositol 3-kinase (PI 3-kinase) activity
immunoprecipitated from a leukemic T cell line by a p85 monoclonal
antibody. A 3-position ring-modified analogue of
D-myo-inositol 1,4,5-trisphosphate
(Ins(1,4,5)P
Volume 270,
Number 20,
Issue of May 19, pp. 12075-12084, 1995
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
), L-chiro-inositol
2,3,5-trisphosphate (L-chiro-Ins(2,3,5)P
)
and its phosphorothioate analogue, L-chiro-inositol
2,3,5-trisphosphorothioate, as well as the analogue benzene
1,2,4-trisphosphate induced reversible inhibition of PI 3-kinase
activity, which correlated with decreased V
but
unchanged Kvalues for PI 3-kinase. Other
inositol phosphates, including D- and
L-Ins(1,4,5)P
, D-myo-inositol
1,3,4,5-tetrakisphosphate, the enantiomers of myo-inositol
1,3,4-trisphosphate, DL-myo-inositol
1,4,6-trisphosphate (DL-Ins(1,4,6)P
), and
DL-scyllo-inositol 1,2,4-trisphosphate
(DL-scyllo-Ins(1,2,4)P
), did not inhibit
PI 3-kinase activity under identical conditions.
L-chiro-Ins(2,3,5)P
closely resembles
Ins(1,4,5)P
and D-Ins(1,4,6)P
except
for a difference in the orientation of a single hydroxyl group at
either the equivalent 3-OH or 2-OH position of Ins(1,4,5)P
,
respectively. Similarly, L-chiro-Ins(2,3,5)P
resembles D-scyllo-Ins(1,2,4)P
, but
has a different orientation of both the equivalent 3-OH and 2-OH
positions. Since Ins(1,4,5)P
,
DL-Ins(1,4,6)P
, and
DL-scyllo-Ins(1,2,4)P
did not inhibit PI
3-kinase activity, this suggests that the orientation of the two
hydroxyl groups at the 2- and 3-positions plays a pivotal role in the
inhibitory action of inositol phosphate analogues on PI 3-kinase
activity. Thus, inositol phosphate analogues inter alia are
shown for the first time to inhibit PI 3-kinase and may be useful tools
for determining the function of PI 3-kinase and its substrate binding
specificities.
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