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( l,4,5)P-3] by vegetative cells, gametes and zygotes of the green alga Chlamydomonas eugametos was studied using a soluble cell fraction as e nzyme source and labelled Ins(1,4,5)P-3 as substrate. This compound wa s dephosphorylated yielding predominantly Ins(l,4)P-2, but in most cel l types Ins(4,5)P-2 could also be detected. Both products were subsequ ently dephosphorylated to Ins(4)P, Ins(l)P and finally inositol. The s tudy demonstrates that in these algae Ins(1,4,5)P-3 is degraded via a pathway that is characteristic of vertebrate rather than higher plant cells.