Close to 15% of the karatasin proteinase activity in the fruit juice of Bromelia plumieri (karatas) is present outside dialysis Visking tubing in 7 days in 0.2 M acetate buffer (pH) 3.5 or 6.5) containing phenyl mercuric acetate. The small proteinase(s), distinct from the 85% activity in juice due to nondialysable karatasin with a reported Mr of 24,868, separates across Spectrapore (13 kDa) membranes but not across Spectrapore with 3.5 kDa average pore diameter. The dialyzed proteinase is named karatasin-D (K-D). Purified non-Dialysable karatasin can be dissociated to what seems to be K-D by incubation in a buffer solution, containing SDS and 2-mercaptoethanol with phenyl mercuric acetate, in dialysis experiments for 8 days at room temperature using Spectrapore 13 kDa tubing. Thus, native karatasin in B. plumieri fruit juice seem to be the result of association of 2 small molecular mass K-D subunits, linked together by disulfide bonds and electrostatic forces, in equilibrium with small amounts of free K-D molecules. The amino acid composition and partial sequence of karatasin up to the 14th position from the amino terminus have discrete analogies with papain and with stem bromelain.
The lectin from Phaseolus acutifolius var. latifolius has been purified to homogeneity by affinity chromatography using stroma-sephadex, gel filtration and electrofocusing. The purified lectin consists of four subunits of 21 Kd molecular mass each one with 7.4% w/w total carbohydrate. Red cells of human and animal species, are agglutinated but are not inhibited by a series of sugars. Mitogenicity and immunosuppressive activities were demonstrated. Agglutination requires magnesium and calcium ions.
Sugar specificity of the Machaerocereus eruca isolectins, MeAI and MeAII, has been determined by comparing the capacity of glycans with well defined structures to inhibit their haemagglutinating activity. Both are galactose-specific isolectins with high affinity for O-glycans. However, the two M. eruca isolectins recognize different oligosaccharidic sequences belonging to O-glycosidically linked glycans from porcine stomach mucin. The minimal structure recognized by MeAI on the porcine mucin glycans is the O-glycan core Gal beta 1,3GalNAc-ol, whereas MeAII has a more extended site and interacts with a biantennary O-glycan possessing the terminal trisaccharide Fuc alpha 1,2 (GalNAc alpha 1,3) Gal beta 1,4.
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