b) MHETase is believed to use a catalytic triad to hydrolyze the ester linkage in MHET, just like the catalytic triad in the serine proteases. Examine the structure of MHETase complexed with the analog and identify the 3 residues in the catalytic triad. For each one, find the most important distance between that residue and its partner in the mechanism and fill out the chart, identifying the 2 atoms used and the distance between them. Also identify the secondary structure in which it is found (e.g., a-helix, ß-strand, tight turn, or loop). Residue (name & #) Ser His Asp Identify the most relevant inter-atomic distance and identify the atom name (click on it in PyMOL) (e.g., "CB" or "C4" or "OG") Atom in Ser: Atom in substrate analog: Atom in His: Atom in Ser: Atom in Asp: Atom in His: distance between atoms (Å) 2° structural context/nWhat other residues in the enzyme are important for binding MHET? Identify at least 4 that seem to play an important role. Residue (chain, name & #) Atom of the residue and the substrate analog? distance Type(s) of interaction (e.g., H-bond, between charge-charge, coordination bond, van der Waals) atoms (Å) 2⁰ structural context Which, if any, of these residues might explain why MHET is a good substrate, but BHET is not? And how would it explain the substrate specificity?

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