Type I, 5'-monodeiodinase activity in the lactating mammary gland
Por:
Aceves C., Valverde -R.C.
Publicada:
1 ene 1989
Resumen:
Mammary homogenates from lactating, weaned, pregnant, and nonpregnant rats were analyzed for 5'-monodeiodinase activity (5'-MA). Only lactating glands exhibited significant enzyme activity. Competitive analysis showed that mammary 5'-MA is not inhibited by high (10 ?M) concentrations of T4 or T3, but is highly sensitive to prophythiouracil (5 mM). Kinetic parameters demonstrate an acompetitive bisubstrate enzymatic mechanism known as the ping-pong type. The K(m) and maximum velocity for rT3 were 0.40 ?M and 1.42 nmol/mg·min, respectively. These results provide the first evidence that 5'-MA is present in the lactating mammary gland and suggest that this enzymatic activity corresponds to type I enzyme.
Filiaciones:
Aceves C.:
Departamento de Fisiologia, Institute de Investigaciones Biomedicas, 04510, United States
|