Subcellular distribution of alanine aminotransferase activity in maize (Zea mays L.) leaves

The intracellular distribution of alanine aminotransferase (AlaAT, EC 2.6.1 .2) activity with L-alanine and 2-oxoglutarate as a substrates in maize who le leaf extract and bundle sheath cells was studied. After isolation of the mitochondrial-peroxisomal fraction, mitochondria and peroxisomes were sepa rated by centrifugation on a linear 40-52 % (w/w) sucrose gradient. L-Alani ne -2-oxoglutarate transaminating activity of whole leaf extract showed two peaks: first distinctly higher associated with mitochondria and second low er with peroxisomes. In bundle sheath cells only one peak of this activity was found. It corresponded to the mitochondrial region of the gradient. It is proposed that mitochondrial L-alanine - 2-oxoglutarate activity was brou ght about by AlaAT. Glycine aminotransferase (EC 2.6.1.4) could be responsi ble for the same activity in peroxisomes.