Immunochemical analysis of nineteen ornithine transcarbamoylase deficiencies

Western blot analysis of 19 human ornithine transcarbamoylase (OTC) deficiencies characterized by neonatal (13 patients: type I) or later onset of symptoms (6 patients: type II) are reported. All the patients studied here are hemizygous males. In the first group, most of the patients had no residual enzymatic activity (11 patients). In 8 cases this is correlated with a complete absence of protein, in 1 patient with a much reduced amount and in 2 others with 80% of an OTC-related protein of normal molecular weight. Only 2 patients with neonatal onset of symptoms had a detectable OTC activity which ranged from 0.5 to 1% of the control. Among the second clinical group of 6 patients with later onset of symptoms, the residual OTC activity was between 5 and 20% at pH 8.0; 3 of them had abnormal kinetics and 50% an OTC-related protein.