Relativistic Effect behind the Molybdenum vs. Tungsten Selectivity in Enzymes

Abstract

: Molybdenum and tungsten being congeners of the 6th group of d-bock elements are similar in many respects in terms of their properties and in fact, both the molybdoenzymes and tungstoenzymes participate in similar type oxotransferase activity in their enzymes. Molybdenum is found as the heaviest essential trace metal in all forms of life but its next heavier congener, tungsten, as the heaviest metal is found only in some prokaryotic organisms. The tungstoenzymes are generally selected by nature for carrying out the low potential redox activities under the anaerobic conditions in the prokaryotic organisms. This nature’s molybdenum vs. tungsten selectivity for their biological functions under different working conditions (surrounding temperature and aerobic/anaerobic environment) is determined mainly by the relativistic effect which is experienced in different extents by these two congeners. Understanding the mechanistic aspects of the relativistic effect controlled enzymatic activities of the tungstoenzymes is of an immense biotechnological interest to develop the eco-friendly and cost effective methods of commercial synthesis of acetaldehyde through hydration of acetylene, and commercial production of hydrogen (H2, a green fuel) by producing the tungsten incorporated nitrogenase (W-N2-ase) in CA6 (mutant strain), and to develop a biomimetic method to replace the hazardous Birch reduction in organic synthesis, etc.