Abstract
NADP+-dependent isocitrate dehydrogenase [IDH: EC 1. 1. 1. 42] was purified to electrophoretic homogeneity from Vibrio parahaemolyticus Y-4, and shown to be a monomeric protein of molecular weight 80, 000 with a pI of 5.0. The amino acid composition and partial sequence at the N-terminus resembled those reported for other bacterial monomeric IDHs. Immunotitration with antisera to the monomeric and dimeric enzymes (antisera to IDH-II and -I of Vibrio ABE-1) showed an immunochemical distinction between the monomeric and dimeric IDHs, but there is similarity within the IDHs of each group. The circular dichroism spectra of the native and heat-denatured enzyme are also similar to those of monomeric IDH (IDH-II of Vibrio ABE-1). These monomeric IDHs are proteins comprising 17-22% helix and 25-35%, β-pleated sheet in the native state.
