Transcript 4 Enzymes in Depth

Enzymes In Depth
With pH!
pH
Enzymes
• Globular proteins
• Built from amino
acids that have acidic
and basic
characteristics
– Amino acids have
both a carboxylic acid
(COOH) and amine
(NH3) groups
Enzymes
• R-COOH  C-COO -1 + H+1
• R-NH3 +1  R-NH2 + H+1
• Ionic bonds
• Increase solution pH can shift equilibrium
• Active sites have R groups
• R groups help substrates attach to active site
• Only works if the arrangement of R groups
interact properly
• +/• H = Hydrogen bonding
• R = Van der Waals bonding
At optimal pH
• Enzyme attaches to substrate with 2 ionic
bonds 
• Groups allow for ionic bonding (caused by a
transfer of H ion from COOH in the side chain
of one amino acid to a NH2 group
Acidic pH
• Nothing will bother the NH3 + but the COO
will want a H ion
– pH (acid = more H ions; basic = more OH ions)
• No ionic bond can form 
Basic pH
• COO- will not be affected
• But NH3+ will lose a H
• No ionic bond will form 