SummaryPyruvate carboxylase (E.C. 6.4.1.1) activity was determined in the circulating peripheral lymphocytes and cultured skin fibroblasts from the family of a patient with hepatic, cerebral, renal cortical, leukocyte, and fibroblast pyruvate carboxylase deficiency (PCp0'"""* deficiency). Lymphocyte activities were: mother, 33-3%; father, 11-2976; brother, 82-103% and sister, 38-48% of the lowest normal. Fibroblasts from the patient's mother and father had 42 and 3496, respectively, of the activity of the lowest normal. These data demonstrate that the disease is inherited in an autosoma1 recessive manner and that lymphocytes and fibroblasts can be used to detect carriers. Neither pyruvate carboxylase nor mitochondrial PEPCK activity in lymphocytes was increased by a 21-hr fast. Speculation plasma (12) and bacteria were negative. The lymphocyte plus monocyte or mixed leukocyte fractions were isolated as described (4) from whole venous blood. Care was taken to eliminate donors that were obese, malnourished, had diabetes mellitus or a family history of the same, were on "unusual" diets or were receiving any medication. Some of the women were, however, taking birth control pills. The donors were instructed that the meal to be eaten before venipuncture should be "balanced" with respect to protein, fat, and carbohydrate. Most donors were assayed for mitochondrial phosphoenolpyruvate carboxykinase (E.C.4.1.1.32, PEPCK) and citrate synthase (E.C.4.1.3.7) in addition to pyruvate carboxylase. Two controls of the same sex and approximate age (controls were about 1 yr older than the patient) as the patient were tested. Pyruvate carboxylase and mitochondria1 PEPCK were assayed by a modification (4) of the methods of Utter and Keech (13) The demonstration that carriers of pyruvate carboxylase defi-3:s'-dithiobis(2-nitrobenzoatd) to mkasure the releasiof free CoAciency can be detected with a venous blood sample may allow, with SH. Protein was determined by the method of Lowry et al. (9). All the use of extensive family studies, the assignment of this enzyme reagents were of the grade and source designated in the earlier to a chromosomal linkage group. publication (4). All blood samplings and assays of suspected carriers of, or patients with pyruvate carboxylase deficiency were accompanied by the simultinkous sampling and assay of a known Pyruvate carboxylase deficiency (2, 3, 6, 71, an inborn error of normal. All skin biopsies and blood samples were obtained with pyruvate metabolism, usually results in severe developmental and informed consent. mental retardation, lactic acidosis and, in at least one case (2, 3) proximal renal tubular acidosis. Until recently, diagnosis of the RESULTS disease has been possible only from a liver biopsy and this has precluded family studies and prenatal diagnosis. However, the The data in Table 1 demonstrate that fasting for 4, 8, or 21 hr recent development by Atkin et 01. (4) of an assay for pyruvate had no significant effect on lymphocyte PYruvate carbox~lase carboxylase in cultured skin fib...
