STUDIES ON THE POLYSACCHARIDE-SULFATING SYSTEM IN SEA URCHIN EMBRYOS

The sulfating system in sea urchin embryos was examined, using the labeled precursor inorganic [³⁵S]sulfate in vivo and [³⁵S]3'-phosphoadenosine 5'-phosphosulfate ([³⁵S]PAPS) in a cell-free system. In vivo incorporation of [³⁵pS]sulfate into the trichloroacetic acid (TCA)-insolubte fraction increased gradually during sea urchin development, whereas radioactivity of [³⁵S]sulfate contained in the TCA-soluble fraction showed a conspicuous peak at the late gastrula stage.
In a cell-free system, the particulate fraction showed marked incorporation of [³⁵pS]JPAPS. This sulfating activity was highest at pH 6.4 to 7.2 and at 27°C, and it was strongly inhibited by Hg ²⁺and p-chloromercuribenzoic acid.
The sulfating activity was quite low in fertilized eggs, but then increased rapidly up to the swimming blastula stage. The activity in the particulate fraction precipitated at 10,000 xg increased gradually and that in the particulate fraction precipitated at 100,000 xg was almost constant from the swimming blastula stage to the pluteus stage.