Abstract:Lectins are a group of proteins of non-immune origin that recognize and bind to carbohydrates without modifying them. Banana is the common name for both herbaceous plants of the genus Musa and for the fruit they produce. They are indeed a promising source for many medicinal applications. Banana lectins have the potential for inhibiting HIV-1 reverse transcriptase activity, suppressing cancer cell proliferation and stimulating macrophage activities. Nevertheless, compared to other plant lectins, there is relatively little information in the literature on banana lectins, particularly with respect to their structure and biological functions. Herein we focus our review on the structure, functions and exploitable properties of banana lectins.

Proteinases have the potential to effect partial solubilization of the proteinaceous gum sericin involved in binding the silk strands together in cocoon, an essential step in the silk cocoon cooking and reeling. Therefore, pineapple extract rich in cysteine proteinases was enzymologically characterized for its potential application in oak tasar (Antheraea proylei J.) silk cocoon cooking and reeling. Optimum sodium carbonate concentration (9.8 mM) and optimum temperature (60ºC) for the proteinase activity were determined. Though relatively thermostable, an enhanced activity loss was observed when the extract was incubated in the temperature range 70-90ºC with sodium carbonate. Bulk of the activity (80-83%) remained after 1 hr of time-dependent inactivation at 60ºC. The tasar cocoon extract neither caused inhibition of the activity nor enhanced its time-dependent loss by incubation at 60ºC. However, it caused an enhanced time-dependent loss of the activity by incubation at 60ºC *Corresponding author with sodium carbonate. Considering these enzymological characteristics, experimental cocooncooking media were constituted by taking the pineapple extract with or without sodium carbonate at room temperature or 60ºC. The results of the cocoon cooking and subsequent single silk filament reeling indicated for an applicability of pineapple extract as an effective agent for the oak tasar cocoon cooking and reeling.The fruit of pineapple, Ananas comosus (L.) Merr. is a rich source of a mixture of cysteine proteinases, the most abundant among them being the fruit bromelain (EC 3.4.22.33) which hydrolytically cleaves the internal peptide bonds in proteins with relatively broad specificity (Rowan and Buttle, 1994). The pineapple proteinases find uses in various industrial and medical applications including brewing, meat tenderization, prevention of diarrhea, digestive aids and treatment of edema (Takagi et al. 1992;Tanabe et al. 1996;Chandler and Mynott, 1998; Kelly, Singh L.R. et al. 1996;Maurer, 2001). The use of enzymes in the silk industry is relatively unexplored, has generated a lot of interest, and much research is being carried out internationally (Gulrajani et al. 2000). Against this background, pineapple fruit pulp extract (simply pineapple extract) having proteinase activity may also find application in tasar silk industry in general and tasar silk cocoon cooking and reeling in particular. The oak tasar (Antheraea proylei J.) silkworm is an important source of tasar silk (Singh and Singh, 1998). The larvae of the silkworm, reared on leaves of oak tree Quercus species (FamilyFagaceae), produce the cocoons from which the tasar silk is reeled (Singh and Singh, 1998). Unlike the mulberry (Bombyx mori L.) silk cocoons, the oak tasar silk cocoons cannot be satisfactorily softened by boiling in plain water (Jolly et al. 1979). The cocoons containing relatively higher amounts of protein-tannin complexes in the form of proanthocyanidins (Pandey and Goel, 1990;Pandey, 1997), have to be softened by more drastic boiling off tech...

A thiol protease was isolated and purified from the crown leaf of pineapple, Ananas comosus (L.) Merr. cv. Queen, by an immunoaffinity procedure. After the purification to electrophoretic homogeneity, the enzyme was characterized with respect to some of its physico-chemical and kinetic properties. The molecular weight of the protease (22.4-22.9 kDa), Km (97 microM) and kcat (8.8 s(-1)) for its esterolytic cleavage of the synthetic protease substrate N(alpha)-CBZ-L-lysine p-nitrophenyl ester, the concentration of its thiol activator L-cysteine required for half maximal activation A0.5 (9.9 microM), optimum pH (6.5) for its proteolytic action on azocasein, T(1/2) (60 degrees C) for inactivation by heating the enzyme (35.5 microg protein/mL) in citrate buffer pH 6.0 for 15 min, and SH-group content (0.98 mol/mol enzyme) were determined. Most of these physicochemical and kinetic properties were found to be similar to those of the already well-characterized stem bromelain (EC 3.4.22.32). Thus, the immunoaffinity purified crown leaf protease appeared to be closely related to stem bromelain.

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A new mannose/glucose specific isolectin VTL-II has been purified to electrophoretic homogeneity from the seeds of Vicia tetrasperma (L.) Schreber through successive steps of (i) lectin extraction, (ii) ammonium sulfate fractionation (30-50%), and (iii) affinity chromatography on a column of Sephadex G-50 covalently coupled with D-mannose. The isolectin was found to be a dimeric protein of molecular weight 62 kDa made up of apparently chemically identical subunits unlike the tetrameric isolectins reported earlier from the same plant source. It was found to exhibit (i) 8-16 times higher specificity for rabbit RBC than human RBC, though it showed unspecificity with respect to the different human blood groups, (ii) non-dependence on divalent metal ion for its hemagglutinating activity, (iii) relatively broad pH optimum ranging from pH 7.0 to 8.0, and (iv) thermal inactivation behavior characterized by t(1/2) of 50 degrees C.