Deuterium oxide as a density label of peroxidases in germinating barley embryos.

Density labeling with deuterium oxide, gel electrophoresis, and isopycnic equilibrium sedimentation were used to study the appearance and disappearance of individual peroxidases in the embryos of germinating barley. No detectable label was incorporated into those peroxidases which are present in the embryo of the dry seed and disappear during germination. Deuterium was incorporated into the additional peroxidases which appeared in the embryo during germination. This incorporation is not due to deuterium-hydrogen exchange into preformed proteins. The results indicate that the newly appearing peroxidases arise by synthesis during germination.