**4. Fabaceae (legume) and Lamiaceae (mint) lectins**

The specific carbohydrate recognition shown by lectins makes them important tools in glycobiology, and, although their physiological role remains unknown, they appear to mediate protein-cell and cell-cell interactions. Lectins are widespread in nature, and most of them have been isolated and characterized from Fabaceae, Gramineae, and Lamiaceae families, among others [47, 48]. Those lectins have been related to insect defense mechanisms, storage proteins, carbohydrate transport, mechanisms of physiological regulation, and mitogenic stimulation processes [49–55]. The ability of the nitrogen-fixing bacteria rhizobia to form a symbiotic relationship with legumes, in which plant root lectins are involved, is well known. The plant-associated bacteria have important effects on plant health and productivity [56–59]. Thus biofilm formation on plants is associated with symbiotic and pathogenic responses, and some root lectins promote this process [60]. The lectins could be a good biotechnological alternative in the control of bacterial biofilms for different purposes, for example, clinical applications [61]. In general, plant lectins have been widely used for studying carbohydrates on cell surface, for typing blood groups, isolating glycoconjugates, and detecting changes in normal oligosaccharide synthesis in tumoral disorders and other pathologies [62–66].

Lectins from Fabaceae have been extensively studied and have a broad specificity for any carbohydrate moieties regardless of having highly conserved amino acid sequences between different species. These proteins have been for a long time a paradigm in the research of interaction protein-carbohydrate and their relationship structure-function [67, 68]. Available sequences (RCSB PDB, UniProtKB/Swiss-Prot) show 20% similarity and 20% of identical amino acids, and conserved amino acids are in the "binding site" and coordinate metal ions [9]. These proteins generally have two or four identical subunits with a molecular weight around 25 kDa; each one contains a binding site for metal ions. A typical example of dimeric lectins belongs to the Viceae tribe. The tetrameric lectins are present in species of the tribe Diocleae, specific by glucose/mannose. In these tribes, many lectins have been isolated and characterized with some biochemical differences and molecular similarities [47]. Recently, subtribe Diocleinae in the Millettioid legumes have been taxonomically tangled together with the large heterogeneous tribe Phaseoleae; however, a comprehensive molecular phylogenetic analysis based on nuclear and chloroplast markers includes all genera ever referred to Diocleae except for the monospecific Philippine *Luzonia*, resolving several key generic relationships within the Millettioid legumes and considered classification of Diocleinae subtribe as a tribe with three main clades: *Canavalia*, *Dioclea*, and *Galactia*. *Canavalia* clade has species gender *Canavalia*; *Dioclea* clade includes *Dioclea*, *Cymbosema*, *Cleobulia* and *Macropsychanthus*; and *Galactia* clade gender has *Galactia*, *Neorudolphia*, *Rhodopsis*, *Bionia*, *Cratylia*, *Lackeya*, *Camptosema*, and *Collaea* [69].

they have been shown to play a role in plant defense [15]. But, plants also express minute amounts of specific lectins as particular responses toward environmental stresses and pathogen attack. In the absence of plant stress, the inducible lectins are not expressed at detectable levels [16]. According that, a central question which has often been asked but up to now not yet been answered definitively is that on the biological function(s) of plant lectins. Several functions have been mentioned, but there is not a final decision about that. However, because of its carbohydrate interactions, lectins have been tested for several biological functions, getting interesting results in some of them. Biological activities are related to immunomodulatory and antitumor [17–19], antifungal [20–23], antiparasitic [24–26], antiproliferative [27–30], healing process [31–33], drug delivery [34–36], as histochemical markers [37–39], biosensors [40, 41], insecticide [42–46], etc.

**Figure 1.** Structural conformation of plant lectins. (A) *Pterocarpus angolensis* homodimer lectin (PDB code (2PHF)). The β-sheet conformation is the most usual in plant lectins (β-sandwich). (B) The carbohydrate recognition domain (CRD) is

The specific carbohydrate recognition shown by lectins makes them important tools in glycobiology, and, although their physiological role remains unknown, they appear to mediate protein-cell and cell-cell interactions. Lectins are widespread in nature, and most of them have been isolated and characterized from Fabaceae, Gramineae, and Lamiaceae families, among others [47, 48]. Those lectins have been related to insect defense mechanisms, storage proteins, carbohydrate transport, mechanisms of physiological regulation, and mitogenic stimulation processes [49–55]. The ability of the nitrogen-fixing bacteria rhizobia to form a symbiotic relationship with legumes, in which plant root lectins are involved, is well known. The plant-associated bacteria have important effects on plant health and productivity [56–59]. Thus biofilm formation on plants is associated with symbiotic and pathogenic responses, and some root lectins promote this process [60]. The lectins could be a good biotechnological alternative in the control of bacterial biofilms for different purposes, for example, clinical

**4. Fabaceae (legume) and Lamiaceae (mint) lectins**

highly conserved in plant lectins, according to its specificity.

22 Insecticides - Agriculture and Toxicology

This tribe is widely distributed throughout the neotropics, and several species from the genus *Dioclea* have been shown to possess a lectin closely related to ConA (lectin type I). The better characterized lectins have been those from *D. grandiflora* [70, 71], *D. lehmanni* Diels [72], and *D. sericea* Kunth [73], among others, all of them belong to the Man/Glc group; their physicochemical properties and structural features are very similar [74].

Studies carried out in the PRG have allowed us to find other lectins having distinct structural and functional properties (named lectin type II) from *Diocleae lehmanni* (DLL), *Dioclea sericea* (DSL), *Dioclea grandiflora* (DGL), *Canavalia ensiformis* (CEL), and *Galactia lindenii* (GLL) [73, 75–77]. These lectins are localized in the same cellular compartment as happens in *D. lehmanni* seeds [78] and have different physicochemical properties; this allow us to question about the physiological role of these proteins. Lectin type II has high affinity toward H type 2 blood group (α-L-Fuc (1–2)-β-D-Gal (1–4)-β-D-GlcNAc-O-R), and the N-terminal region presents a unique sequence hitherto found in some Diocleinae lectins and suggests a functional similarity among this type of lectin which possesses distinctive characteristics differentiating them from "classical" mannose/glucose (Man/Glc) lectins. Taking subunit MW into account, it has been demonstrated that tetrameric forms prevailed in type I lectins, being in fast equilibrium with dimers and monomers whose amount depended upon pH or solution ionic strength [79], while some lectins from type II prevalence dimeric forms (**Table 2**). Despite their high similarity, these ConA-like (type II) lectins could induce different responses in biological assays; for example, when tested for stimulation of human lymphocyte proliferation in vitro, ConBr had a higher proliferation index than ConA, possibly due to minor changes in binding specificities [80].


**Type**

II

*C. ensiformis*

*D.* 

*grandiflora*

*D. lehmanni*

*D. sericea* *G. lindenii*

*C. roseum* *Captosemin*

GalNAc, Me-β-Gal, Lactose

GalNAc and N-acetyl-α-D-lactosamine

N-acetyl-α-D-galactosamine

galactose; Fru, fructose; GalNAc, N-acetyl-α-D-galactosamine.

**Table 2.**

Physicochemical properties of lectins of Diocleae tribe.

Rabbit A+, O+, B+ Abbreviations: kDa, kilodalton; pI, isoelectric point; H-type II, antigen (α-L-Fuc(1–2)-β-D-Gal(1–4)-β-D-GlcNAc-O-R); Man, mannose; Glc, glucose; Me, methyl; Gal,

104

26

65

29

B+, O+ > A+

104,256

26,064

Lactose, sucrose, melibiose

A+, O+, B+

57.27

26.58–30

5.3–

[73]

5.7

8.3

—

—

[139]

Plant Lectins with Insecticidal and Insectistatic Activities http://dx.doi.org/10.5772/intechopen.74962 25

[138]

[137]

Sucrose, melezitose, lactose

A+, O+, B+ > rabbit

58.4

29–30

6.5–

[75]

6.6

H-Type II

Sucrose, melezitose, lactose

Sucrose, melezitose, lactose

A+, O+, B+

58.9

29–30

5.1–

[76]

5.4

A+, O+, B+

57.5

29–30

5.2–

[76]

5.4

**Species**

**Specificity**

**Monosaccharide inhibitor**

**Erythroagglutination**

**Native** 

**Subunits (kDa)**

**pI**

**References**

**(kDa)**

I


**Type**

I

*D.* 

Man/Glc

Man, Glc, Fru

*grandiflora*

*D. lehmanni*

*D. sericea* *D. altisima* *D. violaceae*

*D. rostrata*

*D.* 

*lasiophylla*

*D.* 

Glc; Gal

*sclerocarpa*

*C. ensiformis*

*C. mollis* *C. roseum* *G. lindenii*

Man p-Nitrophenyl-β-D-mannopyranoside, Man

A+, O+

100

29; 60

6,5

[77]

Man, Me-α-fructofuranoside

Glc, Me-α-D-Man

Rabbit Rabbit > A+, O+, B+

Rabbit

96

α:25.5; β:14; γ:12.5

α:30; β:16; γ: 14

α:30; β:18; γ: 12

[136]

8.5–

[135]

8.6

7.1

[67]

Man, Glc, Fru, maltose

Man, Glc, Fru Man, Me-α-D-Man, ovalbumin, fetuin

Rabbit Rabbit

102

α: 25,606; β:12,832;

[134]

γ:12,752

Man, Glc, Fru

Man, Glc, Fru, L-sorbose, Me-α-D-Man, Me-α-D-

Rabbit, A+, O+, B+

A+, O+, B+

Rabbit Rabbit Rabbit, O+ and B+

100

α:26.3; β:14; γ: 9

α:29.5; β:15.8; γ: 11.7

α:30.9; β:15.8; γ: 11.7

α:25,569; β:12,998; γ:

12,588

[67]

[133]

[132]

8.6–

[131]

9.0

57.7

α:29.9; β:16.5; γ: 13.4

6.6–

[73]

6.9

Glc, trehalose

Man, Glc

**Species**

**Specificity**

**Monosaccharide inhibitor**

**Erythroagglutination**

Rabbit

100

α:25–α:26; β:13–β:14;

8.6–9

[70, 71]

γ:8–γ:9

α:25.3; β:14; γ:N.D

8.0– 8.4

[72]

24 Insecticides - Agriculture and Toxicology

**Native** 

**Subunits (kDa)**

**pI**

**References**

**(kDa)**

**Table 2.**Physicochemical properties of lectins of Diocleae tribe.

galactose; Fru, fructose; GalNAc, N-acetyl-α-D-galactosamine.

#### Plant Lectins with Insecticidal and Insectistatic Activities http://dx.doi.org/10.5772/intechopen.74962 25

Lamiaceae lectins have been little studied despite preliminary reports on their ability to recognize the Tn/T antigens [81], normally a cryptic structure in the peptide core of O-glycoproteins and which is widely expressed in several tumors and other disorders such as Tn syndrome and IgA nephropathy [82–85]. The importance of Thomsen-Friedenreich antigen (TF or T, galactose (Gal) β1,3 GalNAcα-O-serine (Ser)/threonine (Thr)) as well as to its precursor, the Tn antigen, and its sialylated forms (sTn) has been reviewed recently [86–91]; according to the above, it is important to have alternatives to study these structures such as the lectins and antibodies. However, a word of caution should be given as accumulating evidence, which has shown that mAbs and lectins do not interact with Tn-containing structures in an identical manner. The observed differences have been ascribed to different Tn-density requirements for the interaction to occur [92].

Detailed studies have been carried out on a very few Lamiaceae species from the Northern hemisphere's temperate zone until now [93–97], and the lectin from *Salvia sclarea* L. seeds (SSL) was the first to be isolated and partially characterized [94]. By contrast, species from the Neotropical *Salvia* subgenus Calosphace Benth have been little explored despite their great diversity. A systematic survey has been conducted on species belonging to the Neotropical Calosphace Benth subgenus [98], and certain species naturalized in the New World have also been investigated [99], some having commercial value. Given the abundance of Lamiaceae species in Colombia and the potential biotechnological applications, our group undertook a systematic search for the identification, isolation, and characterization of lectins from selected species with the determination of their biological activities. The lectins from *S. palifolia* Kunth and *Hyptis mutabilis* (Rich.) Briq. [100] have been partially characterized, and a detailed work has been done with *S. bogotensis* Benth and *Lepechinia bullata* (Kunth) Epling [101, 102].

The importance of these proteins as tools in a variety of biological studies and detection, isolation, structural, and functional properties has been studied, and more recently, T/ Tn-specific lectins have been found in the families Amaranthaceae, Fabaceae, Moraceae, and Orchidaceae, among others. The lectins themselves belong to five families of structurally and evolutionarily related proteins (amaranthines, legume lectins, jacalin-related lectins, type 2 ribosome-inactivating proteins, and GNA-related lectins) [103].

Interestingly, a lectin type I was found in *S. bogotensis* Benth. (SBoL-I) and *Lepechinia bullata* (Kunth) Epling (LBL-I) (such as those found in the tribe Diocleae type I), which recognizes mannose/glucose residues; this fact, together with the molecular properties and highly similar N-terminal regions, led us to propose that lectins type I and type II are two good differentiated groups with structural features proper of legume lectins family, particularly from Diocleae tribe, *Salvia,* and *Lepechinia* genders (**Table 3**) [104]. For these lectins, SDS-PAGE profile was similar to other mannose lectins, a band around 30 kDa with an isoelectric point near to 6.5, and they were able to agglutinate human RBCs from A, B, and O donors. This means that specificity by mannose/glucose moieties or mannose-rich glycan is not a unique feature of any family; conversely, species such as *Galanthus nivalis* (tribe Galantheae) [105] and *Centrolobium microchaete* (tribe Dalbergieae) [106], among others, even species from other families such as Moraceae have mannose/glucose lectins [107].

**Molecular** 

**GLL-I1**

**DLL-I2**

**CRL-I3**

**CEL-I4**

**SBoL-I5**

**LBL-I6**

**properties**

Mr subunit (kDa)7

Mr protein (kDa)8

SDS-page (kDa)

Glycosylation Neutral Sugars (%)

Isoelectric point (PI)

Mannose

150

50

19.5

ND

ND

ND

inhibition

(mM)

Sequence

ND

ADTIVAVELD

ADTIVAVELD

ADTIVAVELD

ADTIVAVELD

ADTIVAVELD

TYPNTDIGDPSYPH

SYPNTDIGDPSYPH

SYPNTDIGDPSYPH

N-terminal

1*Galactia lindenii* lectin type -I (GLL-I) [77].

2*Dioclea lehmanni* lectin type I (DLL-I) [72].

3*Cymbosema roseum* lectin type I (CRL-I) [136].

4*Canavalia ensiformis* concanavalin A (CEL-I) [67].

5*Salvia bogotensis* lectin type I (SBoL-I) [104].

6*Lepechinia bullata* lectin type I (LBL-I) [104].

7Reduced conditions.

8Non-reduced conditions without heat.

Plant Lectins with Insecticidal and Insectistatic Activities http://dx.doi.org/10.5772/intechopen.74962 27

ND, non-determined.

**Table 3.**

Molecular properties of lectins type I from Fabaceae and Lamiaceae families.

 6.15

8.0; 8.13

8.3; 8.42

 ND

1.7–1.9

Si

ND

29, 60

25, 14

100

ND

29

25, 14

ND ND 30, 18, 12

ND ND ND

26.5

106 26, 14, 12.5

No ND

7.1

30–33

ND 30, 60

Si ND

6.5

6.5

ND

Si

30, 60

ND

30–34


Lamiaceae lectins have been little studied despite preliminary reports on their ability to recognize the Tn/T antigens [81], normally a cryptic structure in the peptide core of O-glycoproteins and which is widely expressed in several tumors and other disorders such

antigen (TF or T, galactose (Gal) β1,3 GalNAcα-O-serine (Ser)/threonine (Thr)) as well as to its precursor, the Tn antigen, and its sialylated forms (sTn) has been reviewed recently [86–91]; according to the above, it is important to have alternatives to study these structures such as the lectins and antibodies. However, a word of caution should be given as accumu

lating evidence, which has shown that mAbs and lectins do not interact with Tn-containing structures in an identical manner. The observed differences have been ascribed to different

Detailed studies have been carried out on a very few Lamiaceae species from the Northern

(SSL) was the first to be isolated and partially characterized [94]. By contrast, species from the Neotropical *Salvia* subgenus Calosphace Benth have been little explored despite their great diversity. A systematic survey has been conducted on species belonging to the Neotropical Calosphace Benth subgenus [98], and certain species naturalized in the New World have also been investigated [99], some having commercial value. Given the abun

dance of Lamiaceae species in Colombia and the potential biotechnological applications, our group undertook a systematic search for the identification, isolation, and characteriza

tion of lectins from selected species with the determination of their biological activities. The lectins from *S. palifolia* Kunth and *Hyptis mutabilis* (Rich.) Briq. [100] have been partially characterized, and a detailed work has been done with *S. bogotensis* Benth and *Lepechinia* 

The importance of these proteins as tools in a variety of biological studies and detection, isolation, structural, and functional properties has been studied, and more recently, T/ Tn-specific lectins have been found in the families Amaranthaceae, Fabaceae, Moraceae, and Orchidaceae, among others. The lectins themselves belong to five families of structur

ally and evolutionarily related proteins (amaranthines, legume lectins, jacalin-related lec

Interestingly, a lectin type I was found in *S. bogotensis* Benth. (SBoL-I) and *Lepechinia bullata* (Kunth) Epling (LBL-I) (such as those found in the tribe Diocleae type I), which recognizes mannose/glucose residues; this fact, together with the molecular properties and highly sim

ilar N-terminal regions, led us to propose that lectins type I and type II are two good differ

entiated groups with structural features proper of legume lectins family, particularly from Diocleae tribe, *Salvia,* and *Lepechinia* genders (**Table 3**) [104]. For these lectins, SDS-PAGE profile was similar to other mannose lectins, a band around 30 kDa with an isoelectric point near to 6.5, and they were able to agglutinate human RBCs from A, B, and O donors. This means that specificity by mannose/glucose moieties or mannose-rich glycan is not a unique feature of any family; conversely, species such as *Galanthus nivalis* (tribe Galantheae) [105] and *Centrolobium microchaete* (tribe Dalbergieae) [106], among others, even species from

tins, type 2 ribosome-inactivating proteins, and GNA-related lectins) [103].

other families such as Moraceae have mannose/glucose lectins [107].

–85]. The importance of Thomsen-Friedenreich

–97], and the lectin from *Salvia sclarea* L. seeds








as Tn syndrome and IgA nephropathy [82

26 Insecticides - Agriculture and Toxicology

hemisphere's temperate zone until now [93

*bullata* (Kunth) Epling [101, 102].

Tn-density requirements for the interaction to occur [92].

Plant Lectins with Insecticidal and Insectistatic Activities http://dx.doi.org/10.5772/intechopen.74962 27
