Tenellin biosynthesis

Again, the C-MeT PCR primers were used to obtain a gene probe from gDNA, which was then used to isolated a fused iterative Type I PKS / NRPS from B. bassiana which spears to be involved in tenellin biosynthesis (preliminary evidence from knockout experiments). The PKS/NRPS (hereafter called TENS) is highly homologous to FUSS, but appears to have a functional ER domain. In this synthase the PKS extends 4 times. It methylates and fully reduces after the first condensation, methylates but does not enoyl-reduce after the second condensation, does not methylate or enoyl reduce after the third condensation and does no post-condensation processing at all after the final condensation. Here, evidence from feeding experiments shows that the selected amino acid is tyrosine or phenylalanine (24). 

Scheme 2. Proposed reactions catalysed during the biosynthesis of tenellin 19.

Tenellin.—The recent study on the structure and biosynthesis of tenellin (50) provides a good example of the use of labelling. Firstly, n.m.r. was used in conjunction with biosynthetic labelling of tenellin to provide valuable insight... 

C-16 arise from methionine. Of note is the fact that C-1 of phenylalanine appears at C-4 of tenellin and C-2 at C-6. The implied rearrangement finds analogy in the biosynthesis of tropic acid (51) from phenylalanine. 

Tenellin.—Results of a study on the biosynthesis of tenellin (10), previously reported in a preliminary communication, are now available in a full paper. " New information is that tyrosine is a less efficient precursor than phenylalanine, which indicates that benzene-ring hydroxylation occurs after the phenylalanine has undergone further modification. It is to be noted that incorporation of phenylalanine into tenellin (10) (benzene ring plus carbons 4,5, and 6) involves an intramolecular rearrangement of the phenylalanine skeleton. ... 

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