Abstract
Plants have two types of isocitrate dehydrogenase; one is dependent on NADP (ICDH), while the other uses NAD (IDH).
We have isolated four distinct cDNAs for ICDH in rice, i.e. cytosolic ICDH1-1 and ICDH1-2, chroloplastic ICDH and peroxysomal ICDH. The predicted amino acid sequence of ICDH1-2, chroloplastic ICDH and peroxysomal ICDH was 74-92% identical to the ICDH1-1. Activities of total ICDH were detectable in the extracts from leaf blade(10th position) and spikelets.Total ICDH activity was the highest just after the full expansion of leaf blade and the early stage of ripening of the spikelets. Three distinct cDNAs, i. e. IDHa, IDHb and IDHc for mitochondrial IDH were isolated from rice. IDHa appears to have the catalytic domain, while IDHb and/or IDHc seem the regulatory domains. Cellular localization of IDHa protein showed that the IDHa protein was preferentially detected in the vasucular tissues in leaf blades and in young grain.
