Glucose and other hexoses transporters in marine invertebrates: a mini review

Glucose and related hexoses are very important metabolic substrates. Their most important function is to provide quick fuel for most organisms in all three kingdoms because they are the first substrate for energy production in the form of ATP through glycolysis and the subsequent metabolic pathways. In this paper we review the current information about how glucose and related hexoses are transported across biological membranes to carry out their function either as a metabolic molecule or as energy store in marine invertebrate organisms. In these animals, there are two sugar transport systems that are mediated by the sodium/solute symporter family proteins (SGLT) and the major facilitative super-family proteins (GLUT). The most studied sugar transporters in marine invertebrates are involved with dietary sugar uptake, such as SGLT1, SGLT4, GLUT2 and GLUT5, however more studies need to be done to extend the knowledge about these and other sugar transporters involved in metabolic processes.

The crustacean selenoproteome similarity to other arthropods homologs: a mini review

Selenoproteins (Sels) are involved in oxidative stress regulation. Glutathione peroxidase (GPx) and thioredoxin reductase are among the most studied Sels in crustaceans. Since their expressions and activities are affected by pathogens, environmental and metabolic factors, their functions might be key factors to orchestrate the redox cellular balance. The most studied invertebrate selenoproteome is from Drosophila. In this fly, SelD and SelB are involved in selenoproteins synthesis, whereas SelBthD, SelH and SelK are associated with embryogenesis and animal viability. None of the Sels found in Drosophila have been identified in marine crustaceans yet, and their discovery and function identification is an interesting research challenge. SelM has been identified in crustaceans and is differentially expressed in tissues, while its function remains to be clarified. SelW and G-rich Sel were recently discovered in marine crustaceans and their functions are yet to be clearly defined. To fully understand the crustacean selenoproteome, it is still necessary to identify important Sels such as the SelD, SelBthD and SelB homologs. This knowledge can also be useful for marine crustacean industry to propose better culture strategies, enhanced health and improved profits.

Recombinant expression of marine shrimp lysozyme in Escherichia coli

Shrimp Lysozyme (Lyz) is a key component of the antibacterial response as part of the innate defense in Crustacea; however, it has not been possible to purify this protein because of the very low amount present in the shrimp blood cells (hemocytes). In an effort to produce enough protein to study its function and biochemical properties we have overexpressed Lysozyme from marine shrimp (Penaeus vannamei) in E. coli. A bacterial protein expression system based on the T7 polymerase promoter was used. Although Lyz was produced as insoluble protein in inclusion bodies, its refolding led to an active protein with a yield of ~10 percent. Details of the protein recombinant expression techniques applied to this shrimp protein are presented.