Thunbergia alata

Although the most common unsaturated fatty acids in plants are derived from oleic acid, a wide range of unusual fatty acids are found in the seed oils of different species. Divergent plastid acyl-ACP desaturases have been shown to account for some of this diversity. For example, Coriandrum sativum achieves seed oils rich in A -18 1 (pet-roselinic acid) by desaturation of 16 0 at the A position followed by elongation, while Thunbergia alata attains a similar oil by direct A -desaturation of 16 0. A single acyl-ACP desaturase from Hedera helix can even produce A -dienes (E. Whittle, 2005). 

Gaboon EB, Cranmer AM, Shanklin J, Ohhogge JB. (1994) Delta 6 hexadecenoic acid is synthesized by the activity of a soluble delta 6 palmitoyl-acyl carrier protein desaturase in Thunbergia alata endosperm. 7 Biol Chem 269 27519-27526. 

Present in seed oils of Thunbergia alata and Picramnia sellowii. Also in sea anemones and other marine animals. 

Figure 3.80 Biosynthesis of deutzioside and scabroside from Deutzia (A) and unedoside and stilbericoside from Thunbergia alata (B).

Mutagenesis studies have been conducted to identify amino acids associated with the substrate and regio-specificities of acyl-ACP desaturases. These studies were performed using cDNAs for a A -16 0-ACP desaturase and a A -18 0-ACP desaturase from Thunbergia alata. Based on the activities of chimeric mutants of these enzymes, a 30-amino acid domain was identified that contains determinants for fatty acid chain-length and double bond positional specificities. This domain corresponds to amino acids 178-207 of the A -18 0-ACP desaturase. When this domain was replaced in the A -lbrO-ACP desaturase with the analogous portion of the A -18 0-ACP desaturase, the resulting enzyme catalyzed both the A and A desaturation of 16 0- and 18 0-ACP. 

Grandifloric acid (23) C,5H2209 346.13 -84.0 (MeOH) Thunbergia grandiflora, T. alata (Acanthaceae). [20], T. laurifolia [48]... 

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