Alanine:2-oxoglutarate aminotransferase (EC 2.6.1.2), also called alanine aminotransferase (AlaAT), catalyses transamination reaction between L-alanine and 2-oxoglutarate and the reverse reaction between L-glutamate and pyruvate. It is one of the most important enzymes involved in the synthesis and degradation of L-alanine. There are multiple isoenzymes of this enzyme (2 to 6) present in plants. Subcellular location of these isoenzymes appears to be directly associated with their metabolic role: (i) in C plants (Paniculum miliaceum) alanine aminotransferase participates in the transfer of C units (pyruvate) from mesophyl to bundle sheath cells, (ii) peroxysomal alanine aminotransferase exhibiting L-glutamate : glyoxylate aminotransferase activity is involved in regulation of photorespiration, (iii) alanine aminotransferase lacking L-glutamate : glyoxylate aminotransferase activity participates in hyper- sensitivity response to virus attack and (iv) regulates the alternative oxidase activity in miotchondria. Activation of alanine aminotransferase and simultaneous L-alanine acumulation was observed in plants subjected to hypoxia. On this base it was proposed, that this enzyme is involved in the response mechanisms that allow plants to survive under various adverse conditions such as periodic flooding of fields or lingering of snow cover. Research on transgenic plants also indicated its crutial role in nitrogen metabolism. Moreover peroxysomal alanin aminotransferase capable of using glyoxylate as amino group acceptor appeared to be involved in regulation of serine, citruline and glycine contents in leaves.