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Figure 2.
FIGURE 2. Sequential intersubstrate phosphate transfer
hypotheses for hITPK1. This graphic shows hypothetical
intersubstrate phosphate transfer mechanisms by which levels of
Ins(1,3,4)P[3] could regulate the synthesis of Ins(3,4,5,6)P[4].
Panel A shows the two candidate phosphate carriers with enzyme
represented as "E" with the transferred phosphate highlighted in
red. Panel B expands the nucleotide-mediated phosphate transfer
hypothesis in which enzyme-bound nucleotide acts as the
phosphate carrier. Unliganded ITPK1 is represented by E;
phosphotransferase reactions are indicated by red graphics. The
position of the [^32P] group that is transferred between
inositol phosphates is shown in red.An asterisk indicates a
reaction for which Ins(1,3,4,5)P[4] is also produced at a
reduced rate. We do not rule out the possibility that a
phosphoenzyme intermediate might also participate in these
reactions.
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