PLP is a cofactor for a number of enzymes involved in amino acid metabolism. Give an example of reaction in which PLP participates in cleavage of the a, b, and c bonds of an amino acid, as diagrammed in Fig. 21-8, top right.

Figure 21-8

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Steps 1 & 1': Transimination: H R-C-COO + NH 2-03 PO a-Amino acid H Enzyme 1 (CH) 4 H Enzyme-PLP Schiff base Steps 2 & 2': Tautomerization: CH3 2-03 PO Lys - Enzyme T HN: R-CCOO H-C H CH3 Ketimine H R-C-COO | H-N H H-C 2-03 PO :OH Enzyme (CH) 4 CH3 H Geminal diamine intermediate Lys - Enzyme HNH R -C- 2-0, PO H-C H 2-0PO COO CH3 H a RC COO H-C CH3 2-0,PO H Amino acid-PLP Schiff base (aldimine) Lys-Enzyme I HNH* R-C-COO -Fa H-C+ Enzyme H (CH) 4 NH Resonance-stabilized intermediate CH3