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Lectins are phylogenetically ancient proteins that have specific recognition and binding functions for complex carbohydrates of glycoconjugates, i. e., of glycoproteins, proteoglycans/glycosaminoglycans and glycolipids. This class of proteins mediates important processes of adhesion and communication both inside and outside cells. A large variety of lectins are expressed in the human organism. This article reviews the current knowledge of human lectins with a focus on biochemistry and pathobiochemistry (principles of protein glycosylation and defects of glycosylation as a basis of disease) and cell biology (protein sorting, exocytosis and endocytosis, apoptosis, cell adhesion, cell differentiation, and malignant transformation). The clinical significance of lectin-glycoconjugate interactions is described by example of inflammatory diseases, defects of immune defense, autoimmunity, infectious diseases, and tumor invasion/metastasis. Moreover, therapeutic perspectives of novel drugs that interfere with lectin-carbohydrate interactions are discussed.

In the chorionic plate and stem villi of the human placenta besides the fetal blood vessel system a second extravascular contractile system (EVCS) exists. The cells of this system contain contractile and intermediate filaments and are dipeptidyl peptidase-IV- and NO-synthase-type-I-(NOS)-immunoreactive. Therefore it can be assumed that these cells cleave the vasodilator Substance P (by DPP IV) and produce NO (by NOS) and may contribute to a modulation of the EVCS.

The separation of two molecular forms of liver gamma-glutamyltransferase is achieved by Con A-Sepharose chromatography, an adult type with high affinity to Con A and a fetal type without binding capacity to this lectin. Now we present a new method using micro-columns for affinity chromatography (gel volume 2 ml). By this rapid and inexpensive procedure it is possible to study this enzyme separation for its use in the diagnosis of liver diseases.