Inosinic acid dehydrogenase activity in the Lesch-Nyhan syndrome

Inosinic acid dehydrogenase was evaluated in normal subjects and in patients with the Lesch-Nyhan syndrome. A significant difference in activity was found between erythrocytes derived from normal controls (1.21+/-0.47 pmoles/hr per mg protein) and from 15 patients with the Lesch-Nyhan syndrome (6.72+/-6.23 pmoles/hr per mg protein). However, no difference in activity was demonstrable in muscle or leukocytes derived from normal and Lesch-Nyhan patients. The increased activity of inosinic acid dehydrogenase in erythrocytes from patients with the Lesch-Nyhan syndrome is due to stabilization of the enzyme in vivo as well as the absence of an inhibitor which is present in erythrocytes from normal subjects.