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Characterization of Radical SAM Adenosylhopane Synthase, HpnH, which Catalyzes the 5 ′ ‐Deoxyadenosyl Radical Addition to Diploptene in the Biosynthesis of C 35 Bacteriohopanepolyols
Author(s) -
Sato Shusuke,
Kudo Fumitaka,
Rohmer Michel,
Eguchi Tadashi
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201911584
Subject(s) - biosynthesis , chemistry , flavodoxin , stereochemistry , iron–sulfur cluster , deoxyadenosine , atp synthase , enzyme , stereoselectivity , reductase , biocatalysis , gene cluster , biochemistry , catalysis , reaction mechanism , ferredoxin , gene
Adenosylhopane is a crucial intermediate in the biosynthesis of bacteriohopanepolyols, which are widespread prokaryotic membrane lipids. Herein, it is demonstrated that reconstituted HpnH, a putative radical S ‐adenosyl‐ l ‐methionine (SAM) enzyme, commonly encoded in the hopanoid biosynthetic gene cluster, converts diploptene into adenosylhopane in the presence of SAM, flavodoxin, flavodoxin reductase, and NADPH. NMR spectra of the enzymatic reaction product were identical to those of synthetic (22 R )‐adenosylhopane, indicating that HpnH catalyzes stereoselective C−C formation between C29 of diploptene and C5′ of 5′‐deoxyadenosine. Further, the HpnH reaction in D 2 O‐containing buffer revealed that a D atom was incorporated at the C22 position of adenosylhopane. Based on these results, we propose a radical addition reaction mechanism catalyzed by HpnH for the formation of the C 35 bacteriohopane skeleton.