Researchers have identified a key enzyme in sea urchin egg fertilization. Working on two species of urchins,
Strongylocentrotus purpuratus and
Lytechinus variegatus, Gary Wessel and others at Brown University identified Urchin Dual Oxidase 1 (Udx1), as the enzyme responsible for the typical "respiratory burst" observed at fertilization.
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During this burst, extracellular oxygen is turned into hydrogen peroxide, which is released into the perivitelline space around the egg as part of the metabolic reactions aimed at avoiding polyspermy.