New Insights into the Glycosylation Steps in the Biosynthesis of Sch47554 and Sch47555

Abstract

Sch47554 and Sch47555 are antifungal compounds from Streptomyces sp. SCC-2136. The availability of the biosynthetic gene cluster made it possible to track genes that encode biosynthetic enzymes responsible for the structural features of these two angucyclines. Sugar moieties play important roles in the biological activities of many natural products. An investigation into glycosyltransferases (GTs) might potentially help to diversify pharmaceutically significant drugs through combinatorial biosynthesis. Sequence analysis indicates that SchS7 is a putative C-GT, whereas SchS9 and SchS10 are proposed to be O-GTs. In this study, the roles of these three GTs in the biosynthesis of Sch47554 and Sch47555 are characterized. Coexpression of the aglycone and sugar biosynthetic genes with schS7 in Streptomyces lividans K4 resulted in the production of C-glycosylated rabelomycin, which revealed that SchS7 attached a d-amicetose moiety to the aglycone core structure at the C-9 position. Gene inactivation studies revealed that subsequent glycosylation steps took place in a sequential manner, in which SchS9 first attached either an l-aculose or l-amicetose moiety to 4'-OH of the C-glycosylated aglycone, then SchS10 transferred an l-aculose moiety to 3-OH of the angucycline core.

Baikalomycins A-C, New Aquayamycin-Type Angucyclines Isolated from Lake Baikal Derived Streptomyces sp. IB201691-2A

“…BaiGT3 shows high homology to the C-glycosyltransferases SchS7 (98%), SprGT3 (79%), and UrdGT2 (73%), which catalyze a transfer of the first sugar to the C-9 position of the aglycone. Two other enzymes, BaiGT1 and BaiGT2, are predicted to be O-glycosyltransferases based on their homology to SchS10 (97%) and SchS9 (98%), respectively [30].…”

“…to how it occurs in the case of grincamycins and Sch 47554/47555 biosynthesis [27,30]. At the same time, the function of BaiGT1 remained unclear.…”

“…Similarly, the Sch 47554 and Sch 47555 biosynthetic gene cluster also encode three glycosyltransferases (schS7, schS9 and schS10) [29]. Genetic studies have shown that SchS7 attaches d-amicetose at C-9 and SchS9 further extends the saccharide chain when SchS10 attaches l-aculose at C-3 position [30]. Gene clusters for saprolmycins (spr) and grincamycins (gcn) biosynthesis have been recently cloned and were found to contain three genes encoding glycosyltransferases [27,31].…”

Improved production of antifungal angucycline Sch47554 by manipulating three regulatory genes inStreptomycessp. SCC‐2136

“…The addition of ketoreductase (SchP5), aromatase (SchP4), and cyclase (SchP9) to the mimimal PKS produced UWM6, which was subsequently converted to rabelomycin by an oxygenase (SchP10). Upon another oxygenation step by SchP3, an aglycone backbone was synthesized and further modified by three glycosyltransferases, which resulted in the biosynthesis of Sch47554 and Sch47555 . Additionally, based on the sequence similarity analysis, the sch gene cluster contains several ORFs that may produce genes with a potential regulatory function.…”

Angucycline Glycosides from an Intertidal Sediments Strain Streptomyces sp. and Their Cytotoxic Activity against Hepatoma Carcinoma Cells

“…Although firstly discovered in half a century ago and possessing potent antibacterial, antiproliferative and cytotoxic activities [6][7][8][9][10][11], so far none of angucycline compounds has been successfully developed into clinical drug due to toxicity or solubility issues, which is unlike to its biogenetic relatives tetracycline and anthracycline groups [2]. Recent researches on this group mainly concentrated on the understanding of biosynthetic mechanisms, so as to obtain modified analogues with medicinal potentiality through genetic manipulation [12][13][14].…”