Characterization of human lymphocyte N-acetyltransferase and its relationship to the isoniazid acetylator polymorphism

Characterization of human lymphocyte N-acetyltransferase (NAT) for specific activity, substrate specificity, inhibition, pH optimum, apparent K_m, kinetic mechanism, trypsin stability, freezing stability, and heat stability was carried out in rapid and slow isoniazid (INH) acetylators. There is a statistically significant difference in the heat stability of lymphocyte NAT from rapid and slow INH phenotypes. The lymphocyte enzyme from rapid INH acetylators is less heat stable than the lymphocyte enzyme from slow INH acetylators. This is an indication of a structural, possibly polymorphic, difference in lymphocyte NAT from the two acetylator phenotypes.