Oxidation of [U-14C]Succinic Semialdehyde in Cultured Human Lymphoblasts: Measurement of Residual Succinic Semialdehyde Dehydrogenase Activity in 11 Patients with 4-Hydroxybutyric Aciduria

Abstract

ABSTRACT. The oxidation of [U-14C]succinic semialdehyde to 14C02 has been investigated in cultured lymphoblasts to develop a whole cell assay for succinic semialdehyde dehydrogenase. We have previously demonstrated deficiency of this enzyme in extracts of white cells derived from 13 patients with 4-hydroxybutyric aciduria. Major goals were the demonstration of greater residual succinic semialdehyde dehydrogenase activity in patient cell lines and the better representation of physiology in vivo. In 18 control lymphoblast lines, the conversion of [U-14~succinic semialdehyde to 14C02 was 1579 f 310 dpm. The mean value in lymphoblasts derived from 11 patients with deficiency of succinic semialdehyde dehydrogenase was 112 f 36 dpm approximating 7% of the mean control value. Analysis of organic acids produced from [U-14qsuccinic semialdehyde in control lymphoblasts indicated that 14C02 emanated from the tricarboxylic acid cycle; the major metabolic products were succinic and lactic acids. In the presence of 5mM malonic and 2-propylpentanoic (valproic) acids, I4CO2 production in a control lymphoblast line was decreased by 68 and 45%, respectively. The whole cell assay is less laborious than our previously described assay employing cell extracts, and the general trend was the demonstration of higher residual levels of activity for lymphoblasts derived from patients. (Pediatr Res 24: 455-460, 1988)

Succinic Semialdehyde Dehydrogenase: Biochemical–Molecular–Clinical Disease Mechanisms, Redox Regulation, and Functional Significance

“…The original assay employed to quantify SSADH enzyme activity in white blood cells utilized a coupled system (conversion of radiolabeled GABA to succinate, basically coupling the activities of GABA-transaminase with SSADH), which lacked sensitivity for heterozygote detection or for potential prenatal diagnostic studies (83,138). A significant methodological improvement in enzyme analysis came with the development and implementation of a sensitive fluorometric 692 KIM ET AL.…”

The Clinical Phenotype of Succinic Semialdehyde Dehydrogenase Deficiency (4-Hydroxybutyric Aciduria): Case Reports of 23 New Patients

“…Defi ciency of SSADH activity was demonstrated in extracts of lym phocytes, lymphoblasts, and/or fibroblasts derived from all patients (except P.S.H.). 5 Table) Unless otherwise stated, all pregnancies and deliveries were normal, and children were nondysmorphic with normal somatic growth and no associated movement disorder other than ataxia. Pertinent abnormalities are given.…”

4-Hydroxybutyric aciduria: Further clinical heterogeneity in a new case

“…3-Hydroxypropionic acid, although identified in very small amounts in the patient's urine as a minor component of peak 3, we have also found in normal urine. Adipic acid (peak 14) was present in small amounts and there was no evidence for dicarboxylic aciduria occasionally seen in other patients [1,8].…”

“…The clinical symptoms of six patients have been described in detail, although several others have been diagnosed biochemically [1,4,5,8,9]. From the description of the original cases a rather homogeneous clinical picture emerged mainly characterized by severe psychomotor retardation, hypotonia and nonprogressive ataxia [9].…”