Biochemistry Z 0250 Beyond Carbohydrate Binding: New Directions in Plant Lectin Research -[interaction of plant lectins with non-carbohydrate ligands, especially porphyrins; 150 refs.]. -(KOMATH*, S. S.; KAVITHA, M.; SWAMY, M. J.; Org. Biomol. Chem. 4 (2006) 6, 973-988; Sch. Life Sci., Jawaharlal Nehru Univ., New Delhi 110 067, India; Eng.) -Mischke 28-279

Cold active lipases (CLPs) are gaining importance nowadays as they are increasingly used in fine chemical synthesis, bioremediation, food processing and as detergent additive. These enzymes exhibit high catalytic activity at low temperatures and flexibility to act at low water medium. Since they are active at low temperatures consume less energy and also stabilize fragile compounds in the reaction medium. CLPs are commonly obtained from psychrophilic microorganisms which thrive in cold habitats. Compared to mesophilic and thermophilic lipases, only a few CLPs were studied and industrially exploited so far. CLPs (C. antarctica lipase-A and C. antarctica lipase-B) from Candida antarctica isolated from Antarctic region are the well studied and industrially employed, and many are being followed up. This review updates the CLPs reported recently and the industrial applications of CLPs. ARTICLE HISTORY

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SummaryA galactose-specific lectin has been purified from the seeds of Trichosanthes cordata by affinity chromatography on crosslinked guar gum. The affinity-eluted lectin could be resolved into two isolectins, TCA-I and TCA-II by ion-exchange chromatography on DEAE cellulose. The molecular weights of the isolectins were determined as 59 and 52 kDa by SDS-PAGE. TCA-I is a heterodimer in which the two subunits with masses of 32 and 27 kDa, are covalently connected by disulfide bonds. TCA-I and TCA-II are glycoproteins with 6.2% and 6.8% covalently bound neutral sugar, respectively. CD spectroscopic studies indicate that the two isolectins are very similar in secondary structure and contain about 8 to 10% a-helix, 37-38% b-sheet, 20% b-turns, and 32-33% unordered structures. These isolectins have similar carbohydrate specificities as revealed by hemagglutination-inhibition assays. Carbohydrate specificity, subunit size and composition, and secondary structure of TCA isolectins suggest close similarity to type-II ribosome inactivating proteins. The agglutination activity of TCA-I was found to be highest in the pH range 7.0-8.0. The lectin activity was unaffected between 0 and 408C, but decreased dramatically above 408C. Association constant for the interaction of TCA-I with lactose was determined by monitoring ligand-induced changes in the protein intrinsic fluorescence characteristics as 7.42 3 10 3 M 21 at 258C. The exposure and accessibility of the tryptophan residues of TCA-I and the effect of ligand binding on them have been probed by quenching studies employing neutral and ionic quenchers.