@article { ISI:000237610600013, title = {Purification, characterization and substrate specificity of thermostable alpha-galactosidase from Bacillus stearothermophilus (NCIM-5146)}, journal = {Process Biochemistry}, volume = {41}, number = {6}, year = {2006}, month = {JUN}, pages = {1311-1317}, publisher = {ELSEVIER SCI LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

An extracellular thermostable alpha-galactosidase from Bacillus stearothermophilus (NCIM-5146) has been purified to homogeneity by chromatographic step, using Phenyl Sepharose CL-4B column. The specific activity of the enzyme was increased approximately 389-fold, from 1.03 U/mg protein to 400 U/mg protein. The molecular mass of the purified enzyme as determined by SDS-PAGE and gel filtration was 79.9 and 165.9 kDa, respectively, suggesting dimeric nature. The purified alpha-galactosidase is a non-glycosylated protein with a pI of 4.9. The pH and temperature optima for the purified enzyme are 6.5-7.0 and 65 degrees C, respectively. The alpha-galactosidase is stable over a broad pH range (3-9) and its half-life of inactivation (t(1/2)) at 70 degrees C is 30 min. The partial N-terminal sequence of alpha-galactosidase showed remarkable homology (80\% similarity) with earlier reported alpha-galactosidase from B. stearothermophilus NUB 3621. The secondary structure of the enzyme determined by circular dichroism (CD) spectroscopy exhibited alpha/beta class of protein and showed temperature induced conformational forms below and above the transition temperature. The purified enzyme showed biphasic Arrhenius plot with break point at 55 degrees C for pNPG and 50 degrees C for melibiose, raffinose and stachyose. The enzyme hydrolyzes alpha-1-3, alpha-1-4, and alpha-1-6 galactosidic linkages and not the beta-galactosidic linkages. Synthetic substrates pNPG and oNPG had lower K-m and higher K-cat as compare to natural substrates, melibiose, raffinose, and stachyose. (c) 2006 Elsevier Ltd. All rights reserved.

}, keywords = {alpha-galactosidase, Bacillus stearothermophilus (NCIM-5146), Purification, Secondary structure, thermostable enzyme}, issn = {1359-5113}, doi = {10.1016/j.procbio.2006.01.003}, author = {Gote, M. M. and Khan, Mohammad Islam and Gokhale, D. V. and Bastawade, Kulbhushan B. and Khire, Jayant Malhar} } @article { ISI:000253563900018, title = {Structure-activity relationship of a hemagglutinin from Moringa oleifera seeds}, journal = {International Journal of Biological Macromolecules}, volume = {42}, number = {2}, year = {2008}, month = {MAR}, pages = {203-207}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The hemagglutinin from the seeds of Moringa oleifera (MoL) agglutinates human as well as rabbit erythrocytes; the affinity for the latter is almost 250 times more than that for the former. MoL was inhibited by glycoproteins namely thyroglobulin, fetuin and holotransferin indicating the complex sugar specificity of the lectin. The protein is a homodimer with molecular mass of 14 kDa, subunits (7.1 kDa) linked by the disulfide bond(s). The secondary structure elements of MoL area-helix, 28\%; beta-sheet, 23\%; turn 20\% and unordered 28\%. While the activity and secondary structure were not affected at extreme pH and high temperature, they were drastically affected in presence of dithiothreitol at and above pH 7.0, indicating that disulfide linkages hold the active conformation of the protein. (C) 2007 Elsevier B.V. All rights reserved.

}, keywords = {disulfide linkages, Moringa oleifera hemagglutinin, Secondary structure}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2007.10.024}, author = {Katre, Uma V. and Suresh, C. G. and Khan, Mohammad Islam and Gaikwad, Sushama M.} } @article { ISI:000264484400007, title = {Comparative studies of two araceous lectins by steady state and time-resolved fluorescence and CD spectroscopy}, journal = {Journal of Fluorescence}, volume = {19}, number = {2}, year = {2009}, month = {MAR}, pages = {239-248}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Transitions in the tryptophan microenvironment and secondary structure of two monocot lectins from Sauromatum guttatum and Arisaema tortuosum under different denaturing conditions were studied by steady state and time resolved fluorescence and CD spectroscopy. The lectins exist as tetramers with a single tryptophan residue estimated per monomer, present in a polar environment. Quenching with ionic quenchers showed predominantly electropositive environment for tryptophan residues. Acrylamide had maximum quenching effect. A decrease in KI quenching due to lectin denaturation indicated redistribution of charges as a result of possible conformational change. The two values for lifetimes of tryptophanyl population (1.2-1.4 and 6.3-6.4 ns) reduced substantially on quenching or denaturation. Similarly, both the lectins showed a drastic loss of secondary structure in 5 M Gdn-HCl or 6 M Urea or at pH 2.0 and below. For the first time araceous lectins, like legume lectins are shown to bind adenine. The presence of a compact structure at alkaline pH 10.0-12.0 was observed in CD spectra.

}, keywords = {Araceae lectins, Denaturation, fluorescence, Lifetime spectroscopy, Secondary structure}, issn = {1053-0509}, doi = {10.1007/s10895-008-0409-z}, author = {Dharker, Poorva N. and Gaikwad, Sushama M. and Suresh, C. G. and Dhuna, Vikram and Khan, Mohammad Islam and Singh, Jatinder and Kamboj, Sukhdev Singh} }