Significant improvement from chronic beryllium disease following corticosteroid pulse therapy.

Chronic beryllium disease (CBD) is a rare disease characterized by diffuse interstitial pulmonary granulomatosis. We report a case of CBD which exhibited marked improvement both subjectively and objectively following pulse therapy. The patient was a 36-year-old man whose chief complaint was dyspnea and a dry cough.

Molecular mechanism for pterin-mediated inactivation of tyrosine hydroxylase: formation of insoluble aggregates of tyrosine hydroxylase.

Tyrosine hydroxylase (TH), an iron-containing enzyme, catalyzes the first and rate-limiting step of catecholamine biosynthesis, and requires tetrahydrobiopterin (BH4) as a cofactor. We found that preincubation of recombinant human TH with BH4 results in the irreversible inactivation of the enzyme at a concentration far less than the Km value toward BH4 in spite of its cofactor role, whereas oxidized biopterin, which has no cofactor activity, does not affect the enzyme activity. We show that TH is inactivated by BH4 in competition with the binding of dopamine.

GTP cyclohydrolase I utilizes metal-free GTP as its substrate.

GTP cyclohydrolase I (GCH) is the rate-limiting enzyme for the synthesis of tetrahydrobiopterin and its activity is important in the regulation of monoamine neurotransmitters such as dopamine, norepinephrine and serotonin. We have studied the action of divalent cations on the enzyme activity of purified recombinant human GCH expressed in Escherichia coli. First, we showed that the enzyme activity is dependent on the concentration of Mg-free GTP.