What are the differences between lysine and arginine?

Lysine and arginine are both positively charged amino acids that are mostly present on protein surfaces. There are several differences between lysine and arginine. 

Lysine

• Is a basic amino acid that cannot be synthesized by the human body and is hence an essential amino acid
• Is encoded by codons AAA and AAG
• Has a lysyl side chain
• Provides less stability to proteins because of its geometric structure
• Forms fewer electrostatic interactions in proteins and in one direction only
• pKa value of side chain is 10.54
• Functions – plays a role in proteinogenesis and in epigenetic histone modifications, and helps in the production of carnitine and in crosslinking of collagen polypeptides and uptake of essential minerals 

Arginine

• Is a basic amino acid that can be synthesized in the human body and is hence considered a semi-essential or non-essential amino acid 
• Is encoded by codons CGA, CGC, CGG, CGU, AGA, and AGG
• Has a side chain consisting of a 3- carbon aliphatic straight-chain ending in a guanidino group
• Provides more stability to proteins because of its geometric structure
• Forms a larger number of electrostatic interactions in proteins in three possible directions
• pKa value of side chain is 12.48
• Functions – is the precursor for the biosynthesis of nitric oxide