flavin-mononucleotide and Hypothyroidism

Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Dactinomycin; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Hyperthyroidism; Hypothyroidism; In Vitro Techniques; Iodine Isotopes; Liver; Male; Phosphotransferases; Rats; Riboflavin; Thyroid Hormones; Thyroxine

The means by which thyroid hormone regulates flavocoenzyme biosynthesis was studied in hyper-, eu-, and hypothyroid rats by determining the activities of flavocoenzyme-forming enzymes, viz., flavokinase and FAD synthetase, as well as those of flavocoenzyme-degrading enzymes, viz., FMN phosphatase and FAD pyrophosphatase. Flavokinase activity was increased in hyperthyroid animal and decreased in hypothyroid animals. Correspondence of flavokinase activity with the amount of a high-affinity flavin-binding protein quantitated immunologically in hypo-, eu-, and hyperthyroid rats indicated that the thyroid response is caused by an increased amount of enzyme; moreover, the concomitant decrease in a low-affinity flavin-binding protein suggests an inactive precursor form of flavokinase. FAD synthetase activity showed a similar but less pronounced trend than flavokinase. Activities of FMN phosphatase and FAD pyrophosphatase were not influenced by thyroid hormone. Overall results indicate that the mechanism of thyroid hormone regulation of flavocoenzyme level is in the steps of biosynthesis, especially at flavokinase, rather than in degradation steps.

Topics: Animals; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Hyperthyroidism; Hypothyroidism; Liver; Male; Nucleotidases; Nucleotidyltransferases; Phosphotransferases; Phosphotransferases (Alcohol Group Acceptor); Pyrophosphatases; Rats; Rats, Inbred Strains; Thyroid Hormones

Topics: Animals; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Hypothyroidism; Liver; Male; Rats; Riboflavin Deficiency

Topics: Animals; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Hyperthyroidism; Hypothyroidism; Liver; Male; Nucleotidyltransferases; Phosphoric Monoester Hydrolases; Phosphotransferases; Rats; Thyroidectomy; Thyroxine

Topics: Alcohol Oxidoreductases; Animals; Body Weight; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Glycolates; Hypothyroidism; Liver; Male; Microsomes; NADP; Organ Size; Oxidoreductases; Phosphotransferases; Rats; Riboflavin Deficiency