International Science Community Association Research Journal of Recent Sciences 2277 - 2502 5 2 2016 February 2 Molecular evolution of β Galactosidase in Thermophiles, Psychrophiles, Mesophiles, Plants and Mammals by in silico approach 1 11 EN V. Rani 1 Dept. of Biotechnology, Shoolini University of Biotechnology and Management Sciences, Solan, Himachal Pradesh, India K. Dev 2 > Research Paper 2014 9 14 2016 February 2 To understand adaptation and the evolution at molecular level, -galactosidase was studied among thermophiles, psychrophiles, mesophiles, plants and mammals. Conserved domain analysis revealed that -galactosidase belongs to glycosyl hydrolase family. However, phylogenetic analysis showed higher degree of divergence among bacteria while highly conserved in mammals and plants except Arabidopsis thaliana. 3D modeled structures were studied for interaction with lactose, ONPG, PNPG, glucose, galactose, and ONP. Lactose showed tight binding to all the -galactosidase except in A. psychrolactophilus, where maximum interaction was observed with ONPG. Galactose, glucose and ONP exhibited competitive inhibition for lactose, ONPG and PNPG in H. sapiens, A. psychrolactophilus, and T. african, while un-competitive inhibition for A. thaliana and E. coli. Copyright@ International Science Community Association