Other related information: Lectins and Sugar chains

What are Lectins? 

Lectin is defined by Goldstein ¹⁾ et al. As follows.

• A glyco-binding protein or glycoprotein other than the product of an immune response that aggregates cells or complex carbohydrates.
• It has two or more binding sites and can aggregate animal and plant cells.
• Aggregation is specifically blocked by monosaccharides or oligosaccharides. Generally, lectin is used as a general term for substances having specific binding activity to sugar among proteins or glycoproteins existing in plants, animals, microorganisms, etc.

         References
         1) Goldstein, IJ, Hughes, RC, Monsigny, M., Osawa, T., and Sharon, N., Nature.285,66 (1980)

Classification of lectins

1957 O.D. Mäkelä classified them into four groups according to the coordination of hydroxyl groups at the C-3 and C-4 positions of sugars (Table 1). A lectin classified into Group 4 has not yet been discovered. Recently, the primary structure of lectins has bee It is also classified based on its structure (classification by family) (Table 2).

Table 1 Classification of lectins based on Mäkelä monosaccharide recognition

Mäkelä classification	origin	Common name for lectin	Carbohydrate binding specificity	mitogenic activity
Fuc	gorse	UEA-I	α-L-Fuc	-
Gal Gal NAc	soybeans peanuts castor beans _ _	SBA PNA RCA120 DBA ABA PHA-E PHA-L	α-GalNAc>β-GalNAc β-Gal β-Gal α-GalNAc Galβ1-3GalNAc GalNAc GalNAc	+ ± - - +
D-Man D-Glc D-GlcNAc	jack bean pea lentil fava bean	Con A PSA LCA VFA	α-Man > α-Glc α-Man > α-Glc α-Man > α-Glc α-Man > α-Glc	＋ ＋ ＋ ＋
	pokeweed potato wheat germ gorse	PWM STA WGA UEA-II	GlcNAcβ1-4GlcNAc GlcNAcβ1-4GlcNAc GlcNAcβ1-4GlcNAc GlcNAcβ1-4GlcNAc	+ ± -
L-Glc L-Man	-	-	-	-

Table 2 Classification of lectins by family

Family (Biodistribution)	sugar specificity	major lectins
Legume lectin L-type lectin (plant)	Man Gal Sia Fuc	DSA PHA SBA UEA-I MAM DBA ConA ECA PSA
Monocot lectin M-type lectin (plant)	Mabs	GNA HHA ASA
R-type lectin (animal and plant)	Man Gal Sia Xyl	RCA 120 SSA SNA

Applications of lectins

The table below shows the relationship between diseases and sugar chains. Recently, many glycoproteins and glycolipids that serve as tumor markers have been discovered. These are produced directly by cancer cells themselves or by surrounding cells under the influence of cancer cells, and their quantitative or qualitative changes are applied to diagnosis. For example, since α-fetoprotein (AFP) increases significantly with liver cancer, quantitative changes have long been used for diagnosis. , it is possible to detect cancer at an early stage. In various diseases including cancer, the discovery of new markers and the development of diagnostic methods using them are eagerly awaited and are being actively researched.

Diseases involving sugar chains	Marker or target	Change	Application
liver disease, liver cancer	α-fetoprotein N-type sugar chain ^1)	Increased fucosylated sugar chains Increased LCA binding rate ^2)	Diagnosis by LCA3 ^) 4) 5)
	Transferrin N-glycan	Increased Lex antigen sugar chain6 ^) Increased AAL binding rate7 ^)
	γGTP N-glycan	Increased branching ^8) Increased lactosamine structure	Early diagnosis of cancer
	Cholinesterase N-glycan	Fucose α1-3 increase9 ^) 10)	Diagnose with AAL
alcoholic liver disease	Transferrin N-glycan	Decrease/disappearance11 ^) 12)
choriocarcinoma	hCG N-glycan	Variation of branching13 ^) 14)	Good/Malignant Differentiation
rectal cancer	CEA N-glycans15 ^) 16)	Type I decreased and type II increased High mannose type increased	prognosis
lung cancer	Lacto-based carbohydrate antigen ganglioside	Increased sialyl Lea, Lex17 ^) GM2 expression18 ^)
stomach cancer, colon cancer	Glycolipids19 ^)
pancreatic cancer	CA19-9 etc.	Increased Sialyl Lea20 ^)
	Haptoglobin21 ^)	Increased fucosylated glycans
kidney cancer, bladder cancer	Glycolipid	Increased CDH22 ^)
Uterine cancer	blood group substance	Expression of H-type sugar chain	Spying in UEA, PNA23 ^)
prostate cancer	PSA
ovarian cancer	CA125		Diagnosis by WGA24 ^)
thyroid cancer	Thyroglobulin		Diagnosis at Con A25 ^)
myeloma	IgG N-glycan	reduction of galactose
osteosarcoma, osteoporosis	Bone-type alkaline phosphatase sugar chain ^26) 27)
rheumatoid arthritis	IgG N-glycan28 ^) 29) α1 -acidic glycoprotein N-glycan30 ^)	Reduction of galactose31 ^)	Diagnosis32 ^) 33) 34) 35)
pancreatitis	in serum	Increased 2-6 Sialyl Lea36 ^)
gastritis, enteritis	Glycolipids of mucosal epithelium
leukemia	Ganglioside		Treatment research37 ^) 38)
neuropathy	Ganglioside		therapeutic application
Cataract	Glycolipid	Lex increase39 ^)
Alzheimer's disease	Glycolipids40 ^)	Increase/decrease in amount of glycolipid

Literature

1. Ohno, M., Nishikawa, A., Taniguchi, N., et al., Int. J. Cancer, 51, 315 (1992)
2. Yamashita, K., Taketa, K., et al., Cancer Res., 53, 1 (1993)
3. Taketa, K., Clinical Examinations, 39, 1259 (1995)
4. Nikkei Sangyo Shimbun, 1997.6.10., P19
5. Kuwabara, M., Ariyoshi, Y., Examination and Technology, 27, 443 (1999)