Molecular Characterization and Gene Expression Profiling ... - CUSAT

Chapter 1
lectins and carbohydrates. Some lectins such as BGBP and LGBP have been
suggested to enhance activation of the proPO-system in invertebrates
(Cerenius et al., 1994). BGBP also interacts with an extracellular superoxide
dismutase (SOD) involved in binding with peroxinectin (a cell adhesive and
opsonic peroxidase) to the cell surface. Several agglutinins or lectins have
been detected and characterised in different crustaceans (Soderhall and
Cerenius, 1992; Smith and Chisholm, 1992). However, all the physiologic
roles of lectins in invertebrates remain unclear but it appears that these
molecules are involved in recognition and defense mechanisms against
pathogens and may act as opsonins (Vasta, 1990).
1.6.4.9 Proteinase inhibitors
Many serine proteinase inhibitors have been characterized both in
vertebrates and invertebrates. Most of them fall into well-established families
of proteinase inhibitors such as Kasal, Kunitz, serpins, α-macroglobulins and
metalloproteinase inhibitors (Kanost, 1999). All known serine proteinase
inhibitors in arthropods can be grouped in three mechanistically different
groups: canonical inhibitors (standard mechanism), serpin family and α-
macroglobulin. They are involved in a variety of fundamental physiological
processes, such as blood clotting, innate immune response and embryogenesis
(vertebrates), moulting, metamorphosis and proPO cascades (invertebrates) mainly
to prevent or regulate proteolysis (Simonet et al., 2002).
1.6.4.10 Alpha-2-Macroglobulin-Like (α-2-M) Protein
Shrimp α-2-M protein has been shown to be localized in the
membrane of all haemocyte types and in large vesicular inclusions of the
hyaline and semi-granular cells and possess a key role in mechanisms for
regulation of defense and inflammatory processes (Armstrong et al., 1994).
Although a major and ubiquitous component of blood, the functions of the
α-2-Ms remain largely unresolved. They are known as proteinase inhibitors,
Molecular Characterization and Gene Expression Profiling of Antimicrobial Peptides in Penaeid Shrimps
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