scholarly journals Physiological studies on acid metabolism. 4. Phosphoenolpyruvic carboxylase activity in extracts of Crassulacean plants*

1957 ◽  
Vol 67 (1) ◽  
pp. 73-79 ◽  
Author(s):  
D. A. Walker
Keyword(s):  
Acid Metabolism ◽  
Carboxylase Activity ◽  
Physiological Studies

THIAMINE-RESPONSIVE LACTIC ACIDOSIS IN A PATIENT WITH DEFICIENT LOW-KM PYRUVATE CARBOXYLASE ACTIVITY IN LIVER

PEDIATRICS ◽  
1972 ◽  
Vol 50 (5) ◽  
pp. 702-711
Author(s):  
Michèle G. Brunette ◽  
Edgard Delvin ◽  
Bernard Hazel ◽  
Charles R. Scriver
Keyword(s):  
Lactic Acidosis ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Acid Metabolism ◽  
Psychomotor Retardation ◽  
Dietary Control ◽  
Carboxylase Activity ◽  
Cultured Skin ◽  
Carbohydrate Feeding ◽  
Partial Deficiency

The cause of severe intermittent lactic acidosis was investigated in a female infant with profound psychomotor retardation. Hypoglycemia, hyperpyruvic acidemia, and hyperalaninemia were identified in the newborn period. A triad of lactate, pyruvate, and alanine accumulation persisted throughout infancy, and ACTH, anorexia, and high carbohydrate feeding further provoked their accumulation. Careful dietary control or thiamine-HCl supplementation (5 to 20 mg/day) ameliorated the metabolic abnormality. Pyruvate dehydrogenase activity (which is thiamine-dependent) was normal in leukocytes and cultured skin fibroblasts. Hepatic pyruvate carboxylase activity (which is biotin-dependent) was found to comprise more than one component. There was a partial deficiency of total hepatic pyruvate carboxylase activity in the patient. The loss of activity was confined to the low-Km component of the enzyme which serves pvruvate metabolism in the physiological range. A defect in glucogenesis causing hypoglycemia, pyruvate accumulation with lactic acidosis, and aberrant amino acid metabolism can be attributed to the abnormality of pyruvate carboxylase. The response to thiamine in our patients may reflect activation of a normal "shunt" mechanism for pyruvate disposal via pyruvate dehydrogenase.

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