Q 11-11-33 E

Question

Metabolism of S-adenosylhomocysteine (Section 11-6) involves the following sequence. Propose a mechanism for the second step.

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Answer

The mechanism for the metabolism of S-adenosylhomocysteine is,

1Metabolism of S-adenosylhomocysteine

The metabolism of S-adenosylhomocysteine is done by treating it with a NAD⁺ base, and the leaving group is homocysteine. This process takes place in two steps, first is oxidizing alcohol to the ketone of S-adenosylhomocysteine, and in the second step, homocysteine leaves the compound.

2The mechanism for the metabolism of S-adenosylhomocysteine

In the first step, oxidizes alcohol of S-adenosylhomocysteine to a ketone group and is shown below as,

The mechanism for the metabolism of S-adenosylhomocysteine

3The mechanism for the second step of metabolism of S-adenosylhomocysteine

In the second step, the product formed in the first step is reacted with a base that brings about an E1cB elimination reaction. The leaving group in this is homocysteine.

The mechanism for the second step

Q 11-11-31 E

Q 11-11-34 E

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