Nonpolar hydrophobic amino acids tune the enzymatic activity of lysozyme

We have used five different hydrophobic L-amino acids (Gly, Ala, Val, Leu, Ile) as molecular crowders to investigate their role on the enzymatic activity of lysozyme towards Micrococcus lysodeikticus (M. lys.)cell as substrate. We found that except Ile, all other amino acids show a bell like profile of catalytic efficiency (k_cat/K_m) with their increasing concentration whereas for Ile, the value is gradually increasing. The trend of activation energy (E_a) is also well correlated with the catalytic efficiency of lysozyme. At low concentration of amino acids, soft interaction predominates whereas at higher concentration range, excluded volume, viscosity, hydrophobicity combinedly decrease the activity of lysozyme.