Crystallization and preliminary X-ray structure analysis of isocitrate dehydrogenase from two hyperthermophiles, Aeropyrum pernix and Thermotoga maritima.

Isocitrate dehydrogenase (IDH) catalyses the dehydrogenation and decarboxylation of isocitrate to alpha-ketoglutarate and CO(2) with NAD or NADP as cofactor. IDH from Aeropyrum pernix is the most thermostable IDH identified. Crystals of A. pernix IDH diffracted to 2.6 A with synchrotron radiation and belong to space group P4(3)2(1)2. IDH from Thermotoga maritima is the only IDH that has been characterized as homotetrameric and might be an evolutionary link between two different IDH subfamilies. T. maritima IDH crystals diffracted to 2.8 A with Cu Kalpha radiation and belong to space group P2(1)2(1)2(1). The structures will be helpful in the study of the factors responsible for thermostability and the evolutionary relationships of IDHs.