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The biotransformation of astragalosides by a novel acetyl esterase from Absidia corymbifera AS2

Paper ID Volume ID Publish Year Pages File Format Full-Text
34655 45038 2014 8 PDF Available
Title
The biotransformation of astragalosides by a novel acetyl esterase from Absidia corymbifera AS2
Abstract

•An acetyl esterase was purified and characterized from Absidia corymbifera AS2.•Four peptide fragments of this enzyme were identified by mass spectrometry.•Four astragalosides precursors could be transformed to astragaloside IV (ASI) by the purified enzyme.•The catalytic hydrolysis pathways of astragalosides were clarified.

Absidia corymbifera AS2 has been previously screened for effective biotransformation of astragalosides since it is able to catalyze the hydrolysis of acetyl ester moieties. In this study, an acetyl esterase from A. corymbifera AS2 was purified and its catalytic pathways were investigated. The purified enzyme was monomeric, with a molecular mass of 36 kDa, and with optimal activity observed at pH 8.0 and 35 °C. It was stable within pH 7.0–9.5 and at temperatures lower than 45 °C. The Km and Vmax values for p-nitrophenyl acetate was estimated to be 3.76 and 17.64 mmol (min mg)−1, respectively. We found that this enzyme can hydrolyze the acetyl groups at positions O-2 or O-3 of xylopyranosyl residue at the C-3 position of AS-I, isoAS-I, AS-II and isoAS-II, and convert these all to ASI. The pathways of deacetylation catalyzed by this enzyme were also clarified for the first time: AS-II→ASI, isoAS-II→AS-II→ASI, AS-I→(AS-II, isoAS-II)→ASI and isoAS-I→AS-II→ASI. In summary, an acetyl esterase from A. corymbifera AS2 was extracted, which showed unique enzymatic characteristics and enabled clarification of the biotransformation pathways of astragalosides. This enzyme has potential industrial applications, especially for utilizing abundant astragaloside precursors for the production of rare ASI.

Keywords
Acetyl esterase; Astragalosides; Absidia corymbifera; Purification; MALDI-MS; Biotransformation
First Page Preview
The biotransformation of astragalosides by a novel acetyl esterase from Absidia corymbifera AS2
Publisher
Database: Elsevier - ScienceDirect
Journal: Process Biochemistry - Volume 49, Issue 9, September 2014, Pages 1464–1471
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering