Purification and Characterization of Two Lectins from Aloe arborescens Mill

Abstract

Two lectins have been isolated from leaves of Aloe arborescens Mill by salt precipitation, pH-dependent fractionation and gel filtration. One lectin (P-2) has a molecular weight of approximately 18,000, consists of two subunits (alphabeta) and contains more than 18% by weight of neutral carbohydrate. The smaller subunit (alpha) has a molecular weight of approximately 7,500 and the larger subunit (beta) a molecular weight of approximately 10,500. The other lectin (S-1) has a molecular weight of approximately 24,000, consists of two subunits (gamma2) with a molecular weight of approximately 12,000 and contains more than 50% by weight of neutral carbohydrate. An interesting feature of the amino acid compositions of these lectins is the high proportion of acidic amino acids, such as aspartic acid and glutamic acid, and the low proportion of methionine and histidine. S-1 has a strong hemagglutinating activity. On the other hand, P-2 has not only hemagglutinating activity but also mitogenic activity on lymphocytes, precipitate-forming reactivity with serum proteins, one of which is alpha2-macroglobulin, and complement C3 activating activity via the alternate pathway.

Purification and Characterization of Griffonia simplicifolia Leaf Lectins

“…Until recently, scant attention was given to the purification of leaf lectins, presumably because these plant tissues contain low quantities of lectin. Suzuki et al (28) isolated two lectins from the leaves of Aloe arborescens. These lectins (P-2 and S-1) had mol wt of 18,000 and 24,000, respectively.…”

“…We felt this was worthwhile inasmuch as so few leaf lectins have been isolated and characterized (cf. 28,30). The leaf and seed lectins were compared on the basis of their sugar binding specificity, subunit mol wt, immunological cross reactivity, agglutination of human erythrocytes, and precipitation of glycoconjugates.…”

Pharmacological studies on a plant lectin aloctin A II. Inhibitory effect of aloctin A on experimental models of inflammation in rats.

“…The mechanism of this growth in hibition seemed to be host-mediated. Alo A which is isolated from leaves of Aloe arborescens Mill has many biological activities including mitogenic activity for lymphocytes and cytoagglutination (2,3). Since Aloe arborescens Mill has been known to be used as an anti-inflammatory agent in folklore medicine, we examine in the present paper whether Alo A affects adjuvant arthritis in rats by using the method of Newbould (4) and determine whether Alo A affects car rageenin-induced edema in rats by using the method of Winter et al (5).…”

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“…When Aloe was administered to mice bearing S-180 tumors, the tumor growth was inhibited 91-92 . Similarly, Alexin B, a specific molecule species derived from Aloe, was shown to possess anticancer activity against lymphocytic leukemia 92 .…”