BIO Lecture 3: Enzyme Structure and Function

Enzymes are biomolecules that catalyze chemical reactions.  Most enzymes are proteins (some are RNA too) that fold into specific 3-D structures.  The reason for the importance of folding in enzyme function is the proper formation of the active site (region that is directly involved in catalysis).  

NOTE: Enzymes are most likely to have globular shape

Enzymes work by lowering the activation energy for the reaction.  The active site is responsible for this by using its residues to stabilize the transition state of the reaction.  The active site is very specific for its substrates (the reactants), including stereospecificity (i.e. enzymes catalyzing reactions involving amino acids specific for D or L amino acids).  As an aside, the functional groups in the active site are so carefully arranged that the enzyme can select its substrates from among many others that are similar in size and shape.  

NOTE: In animals, L amino acids and D sugars are found.

Quick note on proteases: they are protein-cleaving enzymes that have an active site with a serine residue whose OH group can act as a nucleophile, attacking the carbonyl carbon of an amino acid residue in a polypeptide chain.  Examples include: trypsin, chymotrypsin, and elastase.  These enzymes are also known for having a recognition pocket (or specificity pocket) near the active site.