A comparison of the two <a href="//commons.wikimedia.org/w/index.php?title=Catalytic_mechanism&amp;action=edit&amp;redlink=1" class="new" title="Catalytic mechanism (page does not exist)">mechanisms</a> used for <a href="//commons.wikimedia.org/w/index.php?title=Proteolysis&amp;action=edit&amp;redlink=1" class="new" title="Proteolysis (page does not exist)">proteolysis</a>. <a href="//commons.wikimedia.org/w/index.php?title=Enzyme&amp;action=edit&amp;redlink=1" class="new" title="Enzyme (page does not exist)">enzyme</a> is shown in black, <a href="//commons.wikimedia.org/w/index.php?title=Substrate&amp;action=edit&amp;redlink=1" class="new" title="Substrate (page does not exist)">substrate</a> protein in red and <a href="//commons.wikimedia.org/wiki/Water" title="Water">water</a> in blue.The top panel shows 1-step <a href="//commons.wikimedia.org/w/index.php?title=Hydrolysis&amp;action=edit&amp;redlink=1" class="new" title="Hydrolysis (page does not exist)">hydrolysis</a> where the enzyme uses an <a href="//commons.wikimedia.org/w/index.php?title=Acid&amp;action=edit&amp;redlink=1" class="new" title="Acid (page does not exist)">acid</a> to <a href="//commons.wikimedia.org/w/index.php?title=Polarise&amp;action=edit&amp;redlink=1" class="new" title="Polarise (page does not exist)">polarise</a> water which then hydrolyses the substrate. The bottom panel shows 2-step hydrolysis where a residue within the enzyme is activated to act as a <a href="//commons.wikimedia.org/w/index.php?title=Nucleophile&amp;action=edit&amp;redlink=1" class="new" title="Nucleophile (page does not exist)">nucleophile</a> (Nu) and attack the substrate. This forms an intermediate where the enzyme is covalently linked to the N-terminal half of the substrate. In a second step, water is activated to hydrolyse this intermediate and complete catalysis. Other enzyme residues (not shown) donate and accept hydrogens and electrostatically stabilise charge build-up along the reaction mechanism.
<a href="//commons.wikimedia.org/wiki/User:Evolution_and_evolvability" title="User:Evolution and evolvability">Thomas Shafee</a>
CC BY 4.0
<span class="int-own-work" lang="en">Own work</span>