Viral Enzyme induction

Fluorohistidine, but not the isomeric 4-fluorohistidine, is a substrate for protein biosynthesis, and is incorporated into bacterial, viral, and mammalian proteins in vitro and in vivo. This difference in behavior may explain in part the fact that the 2-fluoro isomer displays antibacterial, antiviral, and antimalarial activity, while the 4-fluoro isomer is essentially inactive.2-Fluorohistidine also inhibits enzyme induction, presumably as a result of incorporation into protein.Similarly, the dramatic drop in murine leukocyte levels may be related to incorporation of 2-fluorohistidine into murine proteins in vivo. Recent research has exploited the special properties of 2-fluorohistidine to examine the role of histidine residues in the mechanism of anthrax... 

Highly active retroviral therapy (HAART) which consists of inhibitor of viral enzyme (reverse transcriptase (RT) and proteases) which is also a part of biosensor, i.e., induction of inhibitor viral enz5Tne into host and its use as biosensor against HTV [6]. In field of medicine there are nucleic acid biosensor which helps in medical diagnosis [7]. 

These intracellular enzymes remain in an inactive state after their initial induction. They are activated only when the cell comes under viral attack, and their activation can inhibit viral replication in that cell. The 2,5-A synthetase acts in concert with two additional enzymes, i.e. an endori-bonuclease and a phosphodiesterase, to promote and regulate the antiviral state (Figure 8.4). 

Exposure of cells to interferon normally results in the induction of a protein kinase termed eIF-2a protein kinase. The enzyme, which is synthesized in a catalytically inactive form, is activated by exposure to dsRNA. The activated kinase then phosplorylates its substrate, i.e. eIF-2a, which is the smallest subunit of initiation factor 2 (eIF2). This, in turn, blocks construction of the smaller ribosomal subunit, thereby preventing translation of all viral (and cellular) mRNA (Figure 8.6). 

Interferon alfa-n3 is an immnnomodnlator. These small proteins bind to specific cell membranes and initiate complex seqnences, intracellnlar events, inclnding induction of certain enzymes that prodnce antiproliferative action against tumor cells and inhibit viral replication in virus-infected cells. They are used in the treatment of condyloma acuminatum. 

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