Role of thyroid gland on the peroxidase and iodinating enzymes of submaxillary gland.

The peroxidase (EC 1.11.1.7) and iodinase (EC 1.11.1.8) activities of rat submaxillary gland were found to be increased after thyroidectomy. The enzyme activities were maximal on the seventh day after operation and then decreased slightly. However, the enzyme activities were still more than 100% even 28 days following operation. Administration of thyroxine (10mug/100 g body weight) prevented the increase. Puromycin, cycloheximide, and actinomycin D, the inhibitors of protein synthesis, as well as thiouracil partially abolished the increase of activities. These results suggest that thyroxine acts as a regulator of the iodinase and peroxidase enzyme(s) of submaxillary gland,