Dephosphorylation Pathway of D-myo-Inositol 1,4,5-trisphosphate in the Unicellular Green Alga Chlamydomonas eugametos

In vitro dephosphorylation of D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] by vegetative cells, gametes and zygotes of the green alga Chlamydomonas eugametos was studied using a soluble cell fraction as enzyme source and labelled Ins(1,4,5)P3 as substrate. This compound was dephosphorylated yielding predominantly Ins(1,4)P2, but in most cell types Ins(4,5)P2 could also be detected. Both products were subsequently dephosphorylated to Ins(4)P, Ins(1)P and finally inositol. The study demonstrates that in these algae Ins(1,4,5)P3 is degraded via a pathway that is characteristic of vertebrate rather than higher plant cells.