STUDIES ON THE POLYSACCHARIDE-SULFATING SYSTEM IN SEA URCHIN EMBRYOS. I. CHARACTERIZATION OF THE SYSTEM IN SEA URCHIN EMBRYOS*

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Abstract
The sulfating system in sea urchin [Pseudocentrotus depressus, Anthocideris crassipina and Hemicentrotus pulcherrimus] 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 [35S]sulfate into the trichloroacetic acid (TCA)-insoluble 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 [35S]PAPS. This sulfating activity was highest at pH 6.4-7.2 and at 27.degree. C, and it was strongly inhibited by Hg2+ 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 .times. g increased gradually and that in the particulate fraction precipitated at 100,000 .times. g was almost constant from the swimming blastula stage to the pluteus stage.