Question

Due to the interactions with other amino acids in the protein, the pK_a of Glu35 and Asp 52 are both shifted from the standard values found in our table.  The actual pK_a values are 5.9 for Glu35 and 4.5 for Asp52 respectively. Using these pKa values, and the H-H equation, calculate the ratio of deprotonated to protonated side chains for both Glu35 and Asp59 at pH 4.0, pH 5.2 and pH 6.0 (six total calculations).  Using your calculations, clearly explain why the pH optimum of lysozyme lies between pH 4.0 and pH 6.0 and has a “bell” shape.

Due to the interactions with other amino acids in the protein, the pKof Glu35 and Asp 52 are both shifted from the standard values found in our table. The actual pK, values are 5.9 for Glu35 and 4.5 for Asp52 respectively. Using these pKa values, and the H-H equation, calculate the ratio of deprotonated to protonated side chains for both Glu35 and Asp59 at pH 4.0, pH 5.2 and pH 6.0 (six total calculations). Using your calculations, clearly explain why the pH optimum of lysozyme lies between pH 4.0 and pH 6.0 and has a "bell" shape.

Answer 1

From Henderson DH- exet log PH = Pk + – Hasselbalch top . CP) eanation we get I where e DP: de frete nated form Po protonated form) ) logop) - pH-pka 2- Y PH-PK a - 10 [p] when, pH7 pka then only Pl PHK qka then COP) & (P) pt = pka then (PP) = (P] pka of side chain of Glugs & Anp 52 are sol as respective by So At PHY for both [op] . protonated form acill be fore dominant ar pty. The ratio (DP) - 104.590.0126 for Guas At pH set top 104-45 - 0.316 for apse since, s.sk 5.2 So, for Angst the LDP) But, s.2 & So, Sopp for. G 35. The rol The ratio, topi (p= 10 senso. 2 for a COPPP) = 105.2-45 = 5.01 (traspor AL PH6 for beter op te sinn, 46 u gwater than koster PR a. (5.92 4.5) values. De 106.59 - 12.6 for Gemas (D)/(P) = 106-4.5 = 316 for Apps the ratio,

Glasf The active site of lysozgine contain Asb 52. mechanism of lysozyme 6u3s General and dyin HOthe of Glas 0.7 foto way P y UKR Ifot WOK Asp52 $2 # R A Ghe as 0 hott 0 General bare entalpis at of Glas In active site the Arpet remain and defrotonated form & blu 35 out on acid & bare. when, pH 75.9 Then [op) of Guis is redeminent & & when pas. tren Col of a 6luis is predominant. On the other hand when PH L4S then Auf 52 remain ar protonated form (1) which is not desiarable for catalysis in active site. So, optimum octivity of lysozyme lies between PH cok 6.0. Activity & Activity of lysozyme with pH PH