List the amino acid side chains that can accept H+ and those that can donate H+ during enzyme catalyzed reactions.
I have lysine, arginine, and histidine as acceptors and serine, threonine, and tyrosine as donators. Could someone just tell me if those are correct and if I am missing any? Thanks so much!
Yes, those are correct. You have listed all the amino acid side chains that can accept and donate H+ during enzyme catalyzed reactions.
You are correct in identifying lysine, arginine, and histidine as amino acid side chains that can accept H+ during enzyme catalyzed reactions. These amino acids are known as basic residues and have a positive charge at physiological pH.
However, serine, threonine, and tyrosine do not typically donate or accept protons directly during enzyme catalysis. The hydroxyl groups on these residues can participate in hydrogen bonding interactions, but they are not typically involved in accepting or donating protons.
Other amino acid side chains that can donate or accept protons during enzyme catalyzed reactions include:
1. Aspartate (Asp): It can accept protons.
2. Glutamate (Glu): It can accept protons.
3. Cysteine (Cys): It can donate and accept protons.
4. Tyrosine (Tyr): Although not directly involved in proton transfer, the phenolic hydroxyl group of tyrosine can occasionally act as an acid or a base and donate or accept protons.
So, to summarize, the amino acid side chains that can accept protons during enzyme catalyzed reactions are lysine, arginine, histidine, aspartate, and glutamate. The amino acid side chains that can donate and accept protons are cysteine and tyrosine.
Your list is mostly correct, but there are a few side chains that you missed.
Amino acid side chains that can accept H+ (act as acceptors) during enzyme-catalyzed reactions include:
1. Histidine (His): Histidine is unique among the amino acids because it has a side chain with a pKa close to physiological pH (around 7.4). This property allows histidine to accept or donate protons depending on the local pH environment.
2. Lysine (Lys): The side chain of lysine contains a primary amine group that can accept a proton.
3. Arginine (Arg): The side chain of arginine contains a guanidinium group that can accept a proton.
Amino acid side chains that can donate H+ (act as donators) during enzyme-catalyzed reactions include:
1. Serine (Ser): The side chain of serine contains a hydroxyl group that can donate a proton.
2. Threonine (Thr): The side chain of threonine also contains a hydroxyl group that can donate a proton.
3. Tyrosine (Tyr): The side chain of tyrosine contains a hydroxyl group that can also donate a proton.
So, to summarize, the amino acid side chains that can accept H+ are histidine, lysine, and arginine, while the side chains that can donate H+ are serine, threonine, and tyrosine.