Question

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the active site of this enzyme anu 28. A new protease which cleaves the C-terminal amino acid from polypeptide chains and function, in part, by protonating the final peptide bond of the substrate. A pH study showed that drops sharply above pH 8.0 and Km rises sharply above PH 10.5. What amino acids might be present in the active site and what role(s) might they play?

Answer 1

28. For any enzymes pH of a solution exert crucial effects on the structure and activity of enzymes. pH can affect the ionization stte of acidic or basic amino acids. Acidic amino acids having carboxyl functional groups and basic amino acids have amino functional groups in their respective side chains. If pH of reaction medium is altered from its optimum, ionization state of amino acids within active site is altered then the ionic bonds that support 3-D shape of the enzye can be altered. due to this enzyme can loose its activity or altered activity.

If pH of reaction mdium is different from optimum then it affects Vmax and Km of enzyme. Here, in this experiment at pH 8  and 10.5 its Vmax reduces and Km increases respectively. It means, at higher pH affinity of active site with substrate is reduced. (Protonation of polypeptide chain affected). Here, in this study amino cid might be Aspartate or Glutamate.