Involved in biosynthesis of mugineic acid family phytosiderophores. 2-oxoglutarate + nicotianamine = 3''-deamino-3''-oxonicotianamine + L-glutamate Expressed in roots, but not in leaves. By iron deficiency. Only a trace amount of expression is detected when sufficient iron is present. Belongs to the class-I pyridoxal-phosphate-dependent aminotransferase family.