7-keto-8-aminopelargonic

A precursor for biotin, 7-keto-8-aminopelargonic acid, is also prepared by acylation of nitromethane, followed by the selective reduction of the nitro group, as shown in Eq. 5.14.27... 

Keto-8-aminopelargonate synthase 2 adenosylmethionine 7-keto-8-aminopelargonate aminotransferase 3 dethiobiotin synthetase... 

The second nitrogen of biotin is incorporated by transamination of keto-aminopelargonic acid, with S-adenosyfinethionine - an apparently unique metabolic role for thus amino acid derivative that is normally a methyl donor. The immediate product of the deamination of S-adenosylmethionine, S-adenosyl-2-oxo-4-methylthiobutyric acid, is unstable and decomposes non-enzymicaUy to 2-oxo-3-butenoic acid and 5 -methyl tbioadenosine. 

Figure 11.3. Biosynthesis of biotin. Keto-aminopelargonic acid synthase, EC 2.3.1.47 diaminopelargonic acid synthase (aminotransferase), EC 2.6.1.62 dethiobiotin synthase, EC 6.3.3.3 and biotin synthase, EC 2.8.1.6.

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