Isolation of Banana Lectin—a Practical Scale Procedure From Ripe Banana Fruit

Abstract

Banana lectin (BanLec) was isolated from slightly overripe bananas (PCI 6-7) by homogenation in NaCl solution, followed by extraction in the presence of glucose, ammonium sulfate precipitation, and affinity chromatography. Yields were approximately 10-fold greater that those of previously published methods using acidic extraction from very overripe fruit (Peel Color Index [PCI] 7+). By dilution of added isotopically labeled recombinant lectin, the content of total exchangeable BalLec was shown to be constant or to slightly decrease with increasing stage of ripeness, even though extractable BanLec increased, followed by rapid decrease in overripened fruit. In the course of this study we observed that recombinant BanLec expressed in Escherichia coli, although chemically and functionally identical to native BanLec, differed slightly in its apparent molecular size on gel filtration, probably due to differences in its native folding.

Banana Lectin: A Brief Review

“…Original isolation procedures for BanLec adopted traditional affinity chromatography and acetic acid extraction of overripe bananas, presumably because much of the starch has been degraded and the low pH further reduced starch–lectin interaction. However, Wearne et al [16], reported the added disadvantages of this procedure which include a low yield (10 mg/kg) of purified lectin and it may be due to low solubility of the lectin in an acidic medium, and/or to degradation of lectin during the ripening process.…”

“…These sugars are similar or identical to the non-reducing sugar moieties on the SGNPs. This procedure reflects the ability of the nanoparticles, coated with a high density of reactive mannosyl/glucosyl groups, to successfully compete with the starch of banana pulp for binding with the lectin [16,17].…”

“…BanLec, the mannose-specific lectin from banana ( Musa acuminata , or polyploidy hybrid cultivars thereof), recognizes terminal α- d -mannosyl/glycosyl units, internal α-1,3-mannosyl/glucosyl units, and reducing terminal β-1,3-glucosyl units such as those occuring in laminarin, the polysaccharide from the brown alga Laminaria digitata. This specificity renders it of potential value in medicinal applications, such as inhibition of HIV replication through interaction with its gp120 coat glycoprotein, as has recently been demonstrated [16,24].…”

“…The molecular mass and sugar specificity of the recombinant lectin was comparable with the natural banana lectin. However, Wearne et al [16], observed that recombinant BanLec (rBanLec) expressed in Escherichia coli , although chemically and functionally identical to native BanLec, differed slightly in its apparent molecular size, probably because rBanLec may be folded differently from the native protein. This rBanLec is a useful reagent for glycoproteomics and lectin microarrays, with a potential for modulation of the immune response (a potent modulator of the proliferation response in CD3+, CD4+, and CD8+ populations of human PBMCs) [16].…”

Ocorrência e distribuição de BanLec em cultivares de banana e avaliação da sua atividade imunomoduladora in vivo

“…A banana é facilmente encontrada e a preços acessíveis, no entanto, o procedimento de extração e purificação de BanLec proveniente do fruto maduro é desafiador, por causa da grande quantidade de amido presente nesses frutos (MO et al, 2001). Provavelmente por esse motivo, a maioria dos procedimentos de purificação de BanLec realizados até o momento utiliza bananas muito maduras, pois a maior parte do amido já foi degradado em açúcares solúveis, e soluções de extração em faixa de pH muito baixa (KOSHTE et al, 1990;PEUMANS et al, 2000), o que diminuiria a interação amido-lectina (WEARNE et al, 2013). Controle 68,3 ± 7,2 41,8 ± 7,4 58 ± 6,7 45,7 ± 5,3 39,4 ± 7,2 37,2 ± 12,4 4,6 ± 0,4 72,3 ± 5,3 4 ± 1,5 42,8 ± 9,1…”