Zinc was first shown to be required for the growth of the mold Aspergillus niger by Raulin in 1869. Since then, zinc has been demonstrated to be essential for the growth, development and differentiation of all types of life, including microorganisms, plants and animals. After iron, zinc is the second most abundant trace metal in the human body; an average 70-kg adult human contains 2.3 g of zinc. The first zinc metalloenzyme, carbonic anhydrase II (CA3 II, EC 4.2.1.1), was discovered in 1940 by Keilin and Mann. Since then, > 300 zinc enzymes covering all six classes of enzymes and in different species of all phyla have been discovered. The inherent chemical potential and reactivity of zinc are not exceptional compared with those of other metals. However, unlike other first-row transition metals contains a filled d orbital (d10) and therefore does not participate in redox reactions but rather functions as a Lewis acid to accept a pair of electrons. Therefore, the zinc ion is an ideal metal cofactor for reactions that require a redox-stable ion to function as a Lewis acid–type catalyst such as proteolysis and the hydration of carbon dioxide. In the zinc hydrolases and lyases, such as the zinc proteases, the zinc ion serves as a powerful electrophilic catalyst. The metal ion in catalytic enzymatic sites is generally coordinated to three amino acid residues, a combination of histidine, glutamate, aspartate and cysteine. Here you have an example of the coordination of a Zn atom in the inner catalytic core of a metalloprotease, showing the canonical structure involving of two histidines and a glutamate residues.

Structure rendered with @proteinimaging, post-processed with @stylar.ai_official and depicted with @corelphotopaint

#molecularart #protease #zn #catalysis #coordination #his #asp