Isolation, purification and properties of lectin from the seed coat of Mucuna spp.

Abstract

Lectin isolated from Mucuna (cv Ukpo) seed coat was purified by affinity chromatography on porcine thyroglobulin-Sepharose followed by gel filtration.  The purified lectin was found to be homogenous as shown by polyacrylamide gel electrophoresis and its single symmetrical elution from gel filtration.  The molecular mass of the lectin is 20,000 ± 1,500 and is found to be a monomer by SDS gel electrophoresis.  It agglutinated human erythrocytes A, B, O and AB blood group as well as animal erythrocytes.  It is a thermostable glycoprotein which contains 13% carbohydrate and high proportion of acidic and neutral amino acids.  Among the glycoprotein inhibitors tested, porcine thyroglobulin with the sequence of NeuAc (2 - 6/2 - 3) D-Gal B(1 - 4)D-GlcNAc was found to be the most potent inhibitor.  However, its asialo counterpart was not inhibitory.  The lectin was found only in the seed coat even in the immature stage.  The lectin activity declined during maturation and was absent when completely matured and dried.  This study showed that intact seed coat lectin activity was lost on incubation at 37°C for 62 days with 88% loss of water, while similar studies with scraped seed coat showed that the lectin activity was lost in 24 days with 84% dehydration.