Activation of transglutaminase during embryonic development

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Abstract
Incorporation of [3H] putrescine into proteins increased markedly in sea urchin [Arbacia punctulata] eggs upon fertilization. Emitine, an inhibitor of protein synthesis, had no effect on the rate of protein labeling. However, the reaction could be prevented by the addition of 2-[3-(diallylamino)propopionyl]benzothiophene, a noncompetitive inhibitor of transglutaminase, and also by dansylcadaverine, which is a substrate for transglutaminase. The inert N.alpha.-dimethyl analog of dansylcadaverine had no influence. Considering the complexity of the incorporation of the [3H] putrescine tracer in this system, it was deemed essential to prove by rigorous analytical methods that the reaction was consistent with a transglutaminase mechanism. .gamma.-Glutamyl[3H]putrescine could be recovered in 80-90% yield from the proteolytic digest of proteins from the 20-min fertilized cell. Another sign of the in vivo activity of transglutaminase was the isolation of substantial amounts of .alpha.(.gamma.-glutamyl)lysine from proteins of sea urchin embryo, yielding a frequency value for this cross-link as high as 1 mol/400,000 g of protein in the 32-cell-stage material.