Glutaric acidaemia type II (multiple acyl-CoA dehydrogenation deficiency).

The clinical and biochemical phenotype of glutaric acidaemia type II (GAII) has led to the suggestion that the defect in the disorder affects electron transfer from primary FAD-containing dehydrogenases into the respiratory chain. Two proteins are involved in this process, i.e. electron transfer flavoprotein (ETF) and ETF dehydrogenase, an iron--sulphur flavoprotein with a distinctive EPR signal. Reliable catalytic assays for these proteins are not available, but both proteins have been purified and antisera against them prepared in rabbits. SDS-PAG electrophoresis of liver mitochondrial membranes from a GAII infant with congenital anomalies, locating ETF dehydrogenase with specific antiserum, showed no cross-reactive material. EPR of the same membranes showed a marked decrease in the ETF dehydrogenase signal. These results suggest that the defect in GAII in some patients is indeed in electron transport, and specifically in ETF dehydrogenase.