L-Alanine → Acetylpyruvate

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FIG. 13 shows pathways from alanine or ornithine to 2,4-pentadienoate. In Step A of FIG. 13, alanine and acetyl-CoA are joined by AKP thiolase to form AKP. In one pathway, AKP is deaminated to acetylacrlate (Step B). The 4-oxo group of acetylacrylate is then reduced and dehydrated to 2,4-pentadienoate (Steps C/D). In an alternative pathway, AKP is converted to 2,4-dioxopentanoate by an aminotransferase or dehydrogenase (Step E). Reduction of the 2- or 4-oxo group of 2,4-dioxopentanoate yields 2-hydroxy-4-oxopentanoate (Step H) or 4-hydroxy-2-oxovalerate (Step K), respectively. 4-Hydroxy-2-oxovalerate can alternately be formed by the reduction of AKP to 2-amino-4-hydroxypentanoate (Step J) followed by transamination or oxidative deamination (Step L). Once formed, 4-hydroxy-2-oxovalerate can be converted to 2,4-pentadienoate in three enzymatic steps as shown in FIG. 12 (Steps B/C/D of FIG. 12). The 2-hydroxy-4-oxopentanoate intermediate can undergo dehydration to acetylacrylate (Step F) followed by reduction and dehydration (Steps C/D).

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