化学
链霉菌
放线菌
细菌
代谢途径
酶
代谢物
肽聚糖
微生物学
作者
D. Leipold,Gesine Wünsch,M. Schmidt,Hans-Jörg Bart,Thomas Bley,H. Ekkehard Neuhaus,Hannah Bergmann,Elke Richling,Kai Muffler,Roland Ulber
标识
DOI:10.1016/j.procbio.2010.03.013
摘要
Abstract Our studies of the microbial-metabolism of triterpenoid ursolic acid by various Nocardia sp. strains, have led to the proposal of two novel pathways to produce triterpenoid derivatives. Nocardia sp. NRRL 5646, Nocardia sp. 44822 and Nocardia sp. 44000 generated the following ursolic acid derivatives: ursolic acid methyl ester, ursonic acid, ursonic acid methyl ester, 3-oxoursa-1,12-dien-28-oic acid and 3-oxoursa-1,12-dien-28-oic acid methyl ester. Nocardia sp. 45077 synthesized ursonic acid and 3-oxoursa-1,12-dien-28-oic acid while Nocardia sp. 46002 produced only ursonic acid and Nocardia sp. 43069 showed no metabolism at all. The conversion of ursolic acid by Nocardia sp. NRRL 5646 was independent of the medium used for the fermentation. An increase in temperature from 28 °C to 36 °C doubled the reaction rate of the biotransformation. The analysis of ursane metabolites was done by HPLC, while their structures were established using HPLC–APCIpos-MS/MS and HPLC–NMR spectroscopy. The pseudo molecular ion peaks were determined by HPLC–APCIpos-MS and used to measure their molecular weight. The product ion spectra of the metabolites showed the characteristic fragments of Δ12-oleanes and Δ12-ursanes indicating that a substitution in ring A or B was responsible for the decrease in molecular weight. Based on these results, two new biosynthetic pathways are proposed. These new pathways can presumably be used as strategic routes for the biotechnological production of triterpenoid derivatives. It is assumed that a 3β-hydroxysteroid dehydrogenase and a 3-ketosteroid-Δ1-dehydrogenase are involved in the transformation of the steroid.
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