Detection of a catalytic intermediate of peroxidase in hog thyroid microsomes.

A catalytic intermediate, Compound II of peroxidase was detected spectrophotometrically in thyroid microsomes. From comparison with the spectral data on purified thyroid peroxidase, the content of the peroxidase was estimated to be 0.019 nmol per mg of the microsomal protein, being about one-eighth of the amount of cytochrome b5. It was concluded that thyroid peroxidase exhibits the same peroxidase activity for guaiacol or ascorbate in the free and the microsome-bound forms.