Computational investigations on decarboxylase and phosphoribosyltransferase enzymes

Abstract

Proteins are the most essential components of a living system. Their functions range from catalysis, transporting molecules and ions across cell membranes thereby maintaining electrochemical potentials in intra- and extracellular regions, signal transduction, and providing rigidity to cells and tissues. Proteins are constituted by amino acids that are covalently linked to each other to form a polypeptide chain. [1] The primary structure of a protein is the sequence of amino acids along the polymer. To a good extent, the sequence determines the structure of the protein. [2] The long polypeptide chain folds to form local structures, called the secondary structure of a protein. Among several secondary structures of a protein, -helix and -sheet are prominent. Other than these two, there are small 3/10-helices and random coils that connect the -helices and -sheets to produce a proper fold which is the tertiary structure of a protein. [3] In many cases, a number of such tertiary structures associate to form a quaternary structure. A quaternary structure can be formed by the assembling of either homomeric subunits or heteromeric subunits. [1, 3] A typical example of a quaternary structure is hemoglobin consisting of two 2 2-units of myoglobins.