Category Archives: Abhijeet Deb Roy

Glycosyltransferases from Oat (Avena) Implicated in the Acylation of Avenacins

Amorn Owatworakit ; Belinda Townsend ; Thomas Louveau ; Helen Jenner ; Martin Rejzek ; Richard K. Hughes ; Gerhard Saalbach ; Xiaoquan Qi ; Saleha Bakht ; Abhijeet Deb Roy ; Sam T. Mugford ; Rebecca J. M. Goss ; Robert A. Field ; Anne Osbourn

J Biol Chem 2013, 288 (6) 3696-3704

Plants produce a huge array of specialized metabolites that have important functions in defense against biotic and abiotic stresses. Many of these compounds are glycosylated by family 1 glycosyltransferases (GTs). Oats (Avenaspp.) make root-derived antimicrobial triterpenes (avenacins) that provide protection against soil-borne diseases. The ability to synthesize avenacins has evolved since the divergence of oats from other cereals and grasses. The major avenacin, A-1, is acylated with N-methylanthranilic acid. Previously, we have cloned and characterized three genes for avenacin synthesis (for the triterpene synthase SAD1, a triterpene-modifying cytochrome P450 SAD2, and the serine carboxypeptidase-like acyl transferase SAD7), which form part of a biosynthetic gene cluster. Here, we identify a fourth member of this gene cluster encoding a GT belonging to clade L of family 1 (UGT74H5), and show that this enzyme is anN-methylanthranilic acid O-glucosyltransferase implicated in the synthesis of avenacin A-1. Two other closely related family 1 GTs (UGT74H6 and UGT74H7) are also expressed in oat roots. One of these (UGT74H6) is able to glucosylate both N-methylanthranilic acid and benzoic acid, whereas the function of the other (UGT74H7) remains unknown. Our investigations indicate that UGT74H5 is likely to be key for the generation of the activated acyl donor used by SAD7 in the synthesis of the major avenacin, A-1, whereas UGT74H6 may contribute to the synthesis of other forms of avenacin that are acylated with benzoic acid.

 

Gene Expression Enabling Synthetic Diversification of Natural Products : Chemogenetic Generation of Pacidamycin Analogs

Abhijeet Deb Roy ; Sabine Grueschow ; Nickiwe Cairns ; Rebecca J. M. Goss

JACS 2010, 132 (35) 12243-12245

Introduction of prnA, the halogenase gene from pyrrolnitrin biosynthesis, into Streptomyces coeruleorubidus resulted in efficient in situ chlorination of the uridyl peptide antibotic pacidamycin. The installed chlorine provided a selectably functionalizable handle enabling synthetic modification of the natural product using mild cross-coupling conditions in crude aqueous extracts of the culture broth.

An Expeditious Route to Fluorinated Rapamycin Analogues by Utilising Mutasynthesis

Rebecca J. M. Goss ; Simon Lanceron ; Abhijeet Deb Roy ; Simon Sprague ; Mohammed Nur-e-Alam ; David L. Hughes ; Barrie Wilkinson ; Steven J. Moss

ChemBioChem 2010, 11 (5) 698-702

Rapamycin is a drug with several important clinical uses. Its complex structure means that total synthesis of this natural product and its analogues is demanding and lengthy. A more expeditious approach is to utilise biosynthesis to enable the generation of otherwise synthetically intractable analogues. In order to achieve this, rules governing biosynthetic precursor substrate preference must be established. Through determining these rules and synthesising and administering suitable substrate precursors, we demonstrate the first generation of fluorinated rapamycin analogues. Here we report the generation of six new fluororapamycins.

A convenient one-step synthesis of L-aminotryptophans and improved synthesis of 5-fluorotryptophan

Michael Winn ; Abhijeet Deb Roy ; Sabine Grüschow ; Raj S. Parameswaran ; Rebecca J. M. Goss

Bioorg Med Chem Lett 2008, 18 (16) 4508-4510

A one-pot biotransformation for the generation of a series of l-aminotryptophans using a readily prepared protein extract containing tryptophan synthase is reported. The extract exhibits remarkable stability upon freeze-drying, and may be stored and used for long periods after its preparation without significant loss of activity.