Fungal secondary metabolism

Keller N, Turner G, Bennett JW (2005) Fungal secondary metabolism - from biochemistry to... 

Ullan, R.V., Gasqueiro, j., Banuelo, O., Fernandez, F. j., Gutierrez, S., Martin, j. F., A novel epimerization system in fungal secondary metabolism involved in the conversion of isopenicillin N into penicillin N in Acremonium chrysogenum, J. Biol. Chem. 2002, 277, 46216-46225. 

PEREZ-ESTEBAN, B., OREJAS, M., GOMEZ-PARDO, E., PESIALVA, M.A., Molecular characterization of a fungal secondary metabolism promoter Transcription of the Aspergillus nidulans isopenicillin N synthetase gene is modulated by upstream negative elements. Mol. Microbiol., 1993, 9, 881-895. 

PEREZ-ESTEBAN, B., GOMEZ-PARDO, E., PENALVA, M.A., A lacZ reporter fusion method for the genetic analysis of regulatory mutations in pathways of fungal secondary metabolism and its application to the Aspergillus nidulans penicillin pathway, J. BacterioL, 1995,177, 6069-6076. 

The aflatoxin pathway is one of the best-studied pathways of fungal secondary metabolism. Attempts to decipher the pathway began with the discovery of the structure of these toxins. However, the major biochemical steps and the corresponding genetic components of AFBi biosynthesis have been elucidated at a molecular level only in the last decade. Significant progress has been made in deciphering the details of the aflatoxin/ST biosynthetic pathways. " " " " ... 

There are a number of recent reviews of endophytes, both bacterial and fungal, and their secondary metabolism that would provide the interested reader with further details and background. Among these are the excellent reviews concerning the interaction between the endophyte and the host, as well as those that specifically address the bioactive natural product production by endophytic fungi.The latter collectively list over 330 different compounds produced. To the extent that is reasonable, I have chosen not to repeat the information in these recent reviews, but to summarize their findings (Table 1). This review will address the information from the more recent literature and, insofar as is known, details of biosynthesis. 

Inhibition of aflatoxin biosynthesis by neem extracts in fungal cells appear to occur in the very early stages of the biosynthetic pathway (i.e., prior to norsolorinic acid synthesis) because after the initiation of secondary metabolism, the inhibitory effect of the neem leaf constituents was lost (84). 

Batz O, Logemann E, Reinold S, Hahlbrock K. 1998. Extensive reprogramming of primary and secondary metabolism by fungal elicitor or infection in parsley cells. Biol Chem 379 1127-1135. 

Mycotoxins are, in general, low molecular weight, non-antigenic fungal secondary metabolites formed by way of several metabolic pathways, e.g. the polyketide route (aflatoxins), the terpene route (trichothecenes), the amino acid... 

Calvo, A.M., Wilson, R.A., Bok, J.W., Keller, N.P. Relationship between secondary metabolism and fungal development. Microbiol Mol Biol Rev 2002 66 447-459. 

The cyclopropyl group is found as a structural element in a wide range of naturally occurring compounds, in plants and in microorganisms, both fungal and bacterial. In many cases the cyclopropyl functionality is a stable structural entity in secondary metabolites, while in others a cyclopropanoid intermediate is generated transiently as a connecting element between a substrate and a final product both in primary and secondary metabolism. 

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