One reaction catalyzed by PLP dependent enzymes is the decarboxylation of amino
ID: 515100 • Letter: O
Question
One reaction catalyzed by PLP dependent enzymes is the decarboxylation of amino acids. Complete the structure of the "alpha-carbanion" structure which results from the "arrow push" below by showing any missing lone pairs or formal charges. The "alpha-carbanion" structure above is stabilized by delocalization through the PLP to yield what is called the "quinonoid intermediate" shown above. Show "arrow pushes" on your alpha-carbanion structure above which illustrate this delocalization, and which yield structure of the "quinonoid intermediate". The Chem Wiki website which we used in class calls PLP an "electron sink" cofactor. What specific feature of PLP allows it to act as an "electron sink"? The alpha carbon is then reprotonated (by the H-A shown above it). Show "arrow pushes for this step on the quinonoid resonance structure which result in "reprotonated alpha carbon" structure shown above. This structure will then yield the decarboxylated amino acid when it undergoes a(n) ______ reaction. d. In the alpha-carbanion resonance structure above the pyridine ring of the PIP is stable because it is ______ but unstable because it is ______________. e. In the quiononoid resonance structure the pyridine ring is stable because _______ but unstable because ___________.Explanation / Answer
d. In the alpha carbanion resonance structure above the pyridine ring of the PLP is stable because it is aromatic but unstable because positively charged.
e. In the quinonoid resonance structure the pyridine ring is stable because neutral but unstable because of non aromatic.
Note:
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