Question

1. Explain the enzyme kinetics using a labelled graph that shows the impact of environmental changes in pH.   

2. Explain competitive enzyme inhibition. include before and after diagrams along with points

Answer 1

pH denotes the acidity or alkalinity of a solution. Changes in pH usually results in ionization of amino acids, ionizable groups in side chains etc. All this can lead to change in structure and therefore damage the function of proteins. Enzymes are mostly proteins in nature and therefore are affected by changes in pH. Change in pH can affect the ionization state of acidic and basic amino acids. Ionization state changes can interrupt the ionic interactions maintaining the three dimensional structure of the enzyme. Many enzymes lose their activity on very high or very low pH but exhibit maximum activity at a particular pH called as optimum pH of that enzyme. pH can also effect charge and the shape of substrate such that it may not be able to bind to the active site of the enzyme.

Ho Reachan velocity Hraunveyde

Inhibitors are the substances that result in decreased activity of the enzymes. One of the types of inhibitors are competitive inhibitors. A competitive inhibitor is very similar in structure to the substrate of the enzyme and thus it competes with substrate for binding to the enzyme’s active site. On binding to inhibitor, enzyme-inhibitor complex is formed and substrate is unable to bind to the active site of the enzyme. However, effect of competitive inhibitor can be reversed if the substrate concentration is increased. As the substrate concentration is increased, it binds to the active site and rate of reaction reaches maximum. Presence of competitive inhibitor results in increased Km but does not change the Vmax value.

No Inhibitor initial velouty (vo) + Competitie inhibitor k kom kmi Substrate conc. km - no inhibitor kmi - in presence of competine inhibitor

Km is the Michelis-Menten constant, the substrate concentration at which half of Vmax is reached.

Vmax – maximum velocity of the reaction.

As can be seen from figure, apparent Km (Kmi) is increased in the presence of competitive inhibitor as compared to no inhibitor.