Biochemical Evidence for a Putative Inositol 1,3,4,5-Tetrakisphosphate Receptor in the Olfactory System of Atlantic Salmon (Salmo salar)

Table 1

EC₅₀ values for inhibition of IP₄ binding by inositol polyphosphates.

Inositol polyphosphate	EC50
InsP6	42.7 nM
Ins(1,3,4,5,6)P5	316 nM
Ins(3,4,5,6)P4	3.2 μM
Ins(1,4,5,6)P4	31.6 μM
Ins(1,4,5)P3	>100 μM
Ins(1,3,4)P3	>100 μM
Ins(1,4)P2	No inhibition at 10 μM
Ins(4,5)P2	No inhibition at 10 μM

Concentrations of the competing inositol polyphosphate (InsP_𝑥) effective in reducing [³H]IP₄ binding to 50% of the specific binding (EC₅₀) were derived from competition curves as shown in Figure 3. Incubations included 14 nM [³H]IP₄.