Possible explanation for hyperglycinaemia in propionic acidaemia and methylmalonic acidaemia: propionate and methylmalonate inhibit liver and brain mitochondrial clycine transport.

The effect of propionate and methylmalonate on the transport of glycine into rat liver and brain mitochondria was investigated. Both propionate and methylmalonate markedly inhibited mitochondrial glycine transport. These compounds also inhibited 14CO2 production from [14C]glycine by isolated brain and liver mitochondria and glycine metabolism in rat brain cortex slices. These results are discussed with reference to hyperglycinaemia associated wtih propionic acidaemia and methylmalonic acidaemia and as a possible contributory factor to the pathological mechanisms in these conditions.