Homocystinuria: Studies in Tissue Culture

Extract: Cystathionine synthase activities are reported for extracts of fibroblasts grown from 39 control subjects, 47 homocystinuric individuals, and 10 parents of cystathionine synthase-deficient patients. Among the group with homocystinuria, fibroblast extracts from 38 had specific activities of cystathionine synthase below the control range. A number of considerations indicate that these 38 patients excrete homocystine because of cystathionine synthase deficiency. Fibroblasts from nine patients with homocystinuria had specific activities of cystathionine synthase within the control range. This group of nine was shown to be comprised of two individuals with cystathionine synthase deficiency, three with deficient activity of methylenetetrahydrofolate reductase, three with deficient activity of N5-methyltetrahydrofolate-homocysteine methyl-transferase, and one in whom homocystine excretion found by others in earlier studies could not be confirmed during the present investigation. The specific activities in fibroblasts of parents of cystathionine synthase deficient patients in most cases fall near the low end of the control range.