Demonstration of 4‐Aminobutyric acid aminotransferase deficiency in lymphocytes and lymphoblasts

Abstract

AbstractLysates of lymphocytes, isolated from whole blood, and Epstein‐Barr virus transformed cultured lymphoblasts catalysed the transamination of 4‐aminobutyric acid with 2‐oxoglutaric acid as co‐substrate. 4‐Aminobutyric acid aminotransferase activity in lymphocyte and lymphoblast sonicates derived from 12 unrelated control individuals (6 each) was 39 ± 19 pmol min−1 (mg protein−1) (mean ± 1 SD). Activities in lysates of both types of cell derived from a Flemish patient were less than 3% of control. 4‐Aminobutyric acid aminotransferase activity in sonicates derived from the parents and a healthy sibling were 15–37% of the control mean for lymphocytes and 13–20% of the control mean in lymphoblasts, respectively.Km values in a control lymphoblast sonicate were 0.63 and 0.08 mmol L−1 for 4‐aminobutyric and 2‐oxoglutaric acids, respectively. These data indicate that the parents and healthy sibling are heterozygous and the patient is homozygous for a defective gene responsible for 4‐aminobutyric acid aminotransferase deficiency, and that inheritance is autosomal recessive.