Explaining the burst after urchin fertilization

Courtesy of Richard Lockett

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.¹ 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.

"This respiratory burst has been a puzzle since the beginning of the century," says Victor Vacquier from the Scripps Institution of Oceanography in La Jolla, Calif. While other cells that produce peroxide – such as neutrophils – usually do not survive this synthesis, the embryo remains immune to peroxidase. Until now, how this protection occurs remained unclear. Wessel's group used drug inhibitors of the neutrophil respiratory burst...