M. tb ICD-2 is closer to prokaryotic NADP+ ICDs. Rooted neighbour joining phylogenetic tree of M. tb ICD-2 with Thermotoga maritima as outgroup. The numerical values represent the confidence assessed by bootstrap analysis. ICD-2 clusters with NADP+ dependent ICDs of gram-ve bacteria. M. tb ICD-2 has closest homology with Mycobacterium leprae showing 85.4% similarity at protein level. Other close neighbours are human pathogens like Pseudomonas aeruginosa (65%), Vibrio cholerae (60%), Neisseria menengitidis (59%) etc.