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Two mannose-binding lectins, Allium sativum agglutinin (ASA) I (25 kDa) and ASAIII (48 kDa), from garlic bulbs have been purified by affinity chromatography followed by gel filtration. The subunit structures of these lectins are different, but they display similar sugar specificities. Both ASAI and ASAIII are made up of 12.5-and 11.5-kDa subunits. In addition, a complex (136 kDa) comprising a polypeptide chain of 54 ؎ 4 kDa and the subunits of ASAI and ASAIII elutes earlier than these lectins on gel filtration. The 54-kDa subunit is proven to be alliinase, which is known to form a complex with garlic lectins. Constituent subunits of ASAI and ASAIII exhibit the same sequence at their amino termini. ASAI and ASAIII recognize monosaccharides in mannosyl configuration. The potencies of the ligands for ASAs increase in the following order: mannobiose (Man␣1-3Man) < mannotriose (Man␣1-6Man␣1-3Man) Ϸ mannopentaose < < Man 9 -oligosaccharide. The addition of two GlcNAc residues at the reducing end of mannotriose or mannopentaose enhances their potencies significantly, whereas substitution of both ␣1-3-and ␣1-6-mannosyl residues of mannotriose with GlcNAc at the nonreducing end increases their activity only marginally. The best manno-oligosaccharide ligand is Man 9 GlcNAc 2 Asn, which bears several ␣1-2-linked mannose residues. Interaction with glycoproteins suggests that these lectins recognize internal mannose as well as bind to the core pentasaccharide of N-linked glycans even when it is sialylated. The strongest inhibitors are the high mannose-containing glycoproteins, which carry larger glycan chains. Indeed, invertase, which contains 85% of its mannose residues in species larger than Man 20 GlcNAc, exhibited the highest binding affinity. No other mannose-or mannose/glucose-binding lectin has been shown to display such a specificity.The majority of the well characterized plant lectins have been isolated from the seeds of dicotyledonous species. But lectins of non-seed origin from other species are also emerging as promising tools chiefly because of two reasons: (i) a good number of them might contain novel sugar-binding sites; and (ii) they can provide valuable information regarding the biological roles of plant lectins, which to a large extent still remain elusive. In the recent past, there have been several reports of non-seed lectins from monocotyledonous families (1-3), especially Amaryllidaceae. The most remarkable property of these lectins is that they show strict specificity for mannose (2, 4, 5), unlike other mannose/glucose-binding plant lectins. Hence, they are being used extensively as affinity ligands for the purification of glycoproteins, viz. IgM, ␣ 2 -macroglobulin, haptoglobin, and ␤-lipoprotein (3, 6).Van Damme et al. (3) examined a number of species (including Allium sativum) from the family Alliaceae (which is taxonomically close to the family Amaryllidaceae) and found them to accumulate mannose-binding lectins. They observed that lectins from both families share many common properties like their ...

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The kinetics of the binding of mannooligosaccharides to the heterodimeric lectin from garlic bulbs was studied using surface plasmon resonance. The interaction of the bound lectin immobilized on the sensor chip with a selected group of high mannose oligosaccharides was monitored in real time with the change in response units. This investigation corroborates our earlier study about the special preference of garlic lectin for terminal ␣-1,2-linked mannose residues. An increase in binding propensity can be directly correlated to the addition of ␣-1,2-linked mannose to the mannooligosaccharide at its nonreducing end. Mannononase glycopeptide (Man 9 GlcNAc 2 Asn), the highest oligomer studied, exhibited the greatest binding affinity (K a ‫؍‬ 1.2 ؋ 10 6 M ؊1 at 25°C). An analysis of these data reveals that the ␣-1,2-linked terminal mannose on the ␣-1,6 arm is the critical determinant in the recognition of mannooligosaccharides by the lectin. The association (k 1 ) and dissociation rate constants (k ؊1 ) for the binding of Man 9 GlcNAc 2 Asn to Allium sativum agglutinin I are 6.1 ؋ 10 4 M ؊1 s ؊1 and 4.9 ؋ 10 ؊2 s ؊1 , respectively, at 25°C. Whereas k 1 increases progressively from Man 3 to Man 7 derivatives, and more dramatically so for Man 8 and Man 9 derivatives, k ؊1 decreases relatively much less gradually from Man 3 to Man 9 structures. An unprecedented increase in the association rate constant for interaction with Allium sativum agglutinin I with the structure of the oligosaccharide ligand constitutes a significant finding in protein-sugar recognition.The structurally and evolutionarily related monocot mannose-binding proteins comprise a superfamily of mannose-specific lectins. Amaryllidaceae, Alliaceae, Araceae, Orchidaceae, Iridaceae, and Liliaceae families have been shown to possess these bulb lectins (1). Among the unique features that set them apart from the Glc/Man/Gal-specific family of dicotyledonous legume lectins and the C-type mannose-binding animal lectins is their high degree of stereospecificity for mannose, so much so that they show no binding propensity even for its epimer, glucose, or the conformationally related analog, L-fucose. Their classification into the mannose-specific lectin family is corroborated by determination of the crystal structures of snowdrop (Galanthus nivalis) (2), daffodil (Narcissus pseudonarcissus) (3), bluebell (Scilla campanulata) (4), amaryllis (Hippeastrum hybrid) (5), and garlic (Allium sativum) lectin (6), representatives of the family of bulb lectins. Their subunits have been observed to possess a novel 3-fold symmetry having three fourstranded antiparallel ␤-sheets arranged as three sides of a triangular prism, forming a 12-stranded ␤-barrel referred to as the ␤-prism II fold. These 12 strands are positioned perpendicular to the plane of symmetry, unlike the other known all-␤-folds: ␤-prism I (e.g. Jacalin; (7)) and the ␤-trefoil (e.g. amaranthin; (8)) fold (6). The central region in the ␤-barrel is stacked with conserved hydrophobic side chains, which stabilize th...

Management of diabetes is a challenge starting in the pre-analytical phase with selecting the most appropriate glycolysis inhibitor. Study goal was to calculate the impact of tubes with different glycolysis inhibitors on the classification of the glycemic control of 157,415 consecutive hospital patients according to current WHO diabetes criteria.MethodsGlucose and lactate were measured in parallel in samples from 68 healthy subjects collected and stored in different sample tubes from Sarstedt and Greiner. Bias to baseline conditions (fluoride heparin (FH) tubes, centrifugation within 1 h) was determined.ResultsIn baseline samples, glucose concentration in fluoride/EDTA/citrate (FC) plasma was ~13% higher and lactate concentration ~20% lower compared to FH, fluoride oxalate, and fluoride EDTA plasma, and in serum. Glucose recovery after storage up to 48 h was 99–101% in the different tubes, but the effectiveness of glycolysis inhibition by FC was inconsistent. Based on the observed mean bias of 12% when FC tubes are used, we estimate an increase of 48.4–55.8% in the frequency of patients with impaired glucose levels using current WHO criteria.ConclusionUsing current established decision limits, the number of patients with impaired glucose levels in the hospital would increase substantially with a strong impact on patient treatment and consumption of resources. The unpredictable failure of glycolysis inhibition in FC tubes does not allow to adjust the decision limits by a fixed factor. In the absence of prospective outcome studies with FC tubes, we recommend to measure glucose in samples containing FH.