Kinetic characterization of thyroid peroxidase enzyme and its inhibition by autoantibodies.
A guaiacol method was developed to measure thyroid peroxidase (TPO) activity and the inhibitory effect of anti-TPO antibodies using purified porcine TPO. The TPO preparation was characterized kinetically and identified by western-blotting technique. The K(M) for guaiacol determined in vitro was 5.6 x 10(-4) M. Investigating the effect of IgG's from 23 hypothyroid patients on TPO activity inhibition was detected in 15 cases with the guaiacol method. It was found that anti-TPO antibodies exerted a competitive inhibition TPO activity with respect to the substrate guaiacol. The inhibition is carried by IgGF(ab')2 fragment. We wanted to gain a method which is interpreted immunologically and can be well employed in the clinical practice.
Kaczur
V
V
Department of Pathology, Kenézy Teaching Hospital, Debrecen, Hungary.
Vereb
G
G
Molnár
I
I
Krajczár
G
G
Balázs
C
C
D000818:Animals; D001323:Autoantibodies / Q000276:immunology*; D006139:Guaiacol / Q000378:metabolism; D006801:Humans; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D013552:Swine
D001323:Autoantibodies; D006139:Guaiacol; D007453:Iodide Peroxidase