I conditions, many essential biochemical reactions proceed so slowly that life c

Question

I conditions, many essential biochemical reactions proceed so slowly that life could not exist der t without the presence of enzymes. Enzymes increase reaction rates through a wide variety of mechanisms These mechanisms generally utilize the following strategies: improving the nucleophiles and electrophiles present in the catalytic R groups or substrates; stabilizing the extra electron density of the leaving group and stabilizing transition states Proteases are that break down proteins by hydrolyzing peptide bonds. Chymotrypsin is a rotease found in the digestive tract that cleaves peptide bonds on the C-terminal side of hobic amino acids Depicted below are a peptide substrate and the three catalytic residues within the chymotrypsin active site Note that the 2-dimensional geometry is only roughly shown. R1 represents a large hydrophobic amino acid and R represents other amino acids. The R groups of the catalytic triad of aspartate (Asp102), serine (Ser195), and histidine (His57) are shown. Select the atoms that act as nucleophiles and electrophiles in the acylation phase of the reaction. Scroll down for more of this question. Note: Selected atoms will turn green (undo by clicking again) Select the 2 atoms that act as nucleophiles in the acylation phase. Note: As shown below, the nucleophilic atoms might be weak nucleophiles, but they become strong in the process of catalysis. Select the 2 atoms that act as electrophiles in the acylation phase

Explanation / Answer

The alkoxide ion on serine 195 is stabilized by hydrogen bonds with backbone amide group

the hydrogen bond network among the catalytic triad orients His 57 and Ser 195 for proton transfer .

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