1. What is the best description of the \"oxyanion hole\" generated during the me

Question

1. What is the best description of the "oxyanion hole" generated during the mechanism of a serine protease catalyzed reaction? a. the oxyanion hole is generated as a result of deprotonation of the serine by a neighboring histidine, resulting in a negatively charged oxygen nucleophile b. the oxyanion hole describes the binding pocket for the phenylalanine amino acids that are preferred substrates for the serine proteases c. the oxyanion hole describes the stabilization of the tetrahedral intermediate where H bonding lowers the energy of the negatively charged oxygen resulting from nucleophilic attack on the carbonyl carbon d. the oxyanion hole describes the planar enzyme-substrate intermediate formed as the carbonyl double-bond is reformed 2.Which statement describes a common feature of both the RNase A and Serine Protease mechanisms? a.A deprotonated serine acts as a nucleophile b. a covalent enzyme-substrate intermediate is formed c. Water is protonated by a Histidine to generate an acidic hydronium ion d. a Histidine acts as a Bronsted base to remove a proton from an alcohol group

Explanation / Answer

1) answer is d)the oxyanion hole describes the planar enzyme substrate intermediate formed as the carbonyl double bond is reformed.

The oxyanion hole is the result of formation of Gly193 and Ser195.t thes both donate the hydrogen atoms for bonding as a backbone.i n tetrahedral intermediate step 1and step 3.the oxygen of carbonyl group accepts the electron and forms the double covalent bond and hence the bond is reformed.

2)the answer is a)a deprotonated serine acts as a nucleophile.

I have solved this answer by the way of elimination .acovalenta enzyme can not be formed as the ions qreanot shared rather the ions are donated so it is aionica bond and hence option b is eliminated.

H - is generated but it doesnt bind with water instead it donates its electrons to be stable and option c is not tgetanswwer.

Alcohol group is not present as hydrogen n carboxyl group form a bond and hence option d is incorrect.

And hence answer is a

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