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Exploring the Biocatalytic Scope of Alditol Oxidase from Streptomyces coelicolor
Author(s) -
van Hellemond Erik W.,
Vermote Linda,
Koolen Wilma,
Sonke Theo,
Zandvoort Ellen,
Heuts Dominic P. H. M.,
Janssen Dick B.,
Fraaije Marco W.
Publication year - 2009
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200900176
Subject(s) - chemistry , streptomyces coelicolor , substrate (aquarium) , enantiomeric excess , enantioselective synthesis , cofactor , stereochemistry , enzyme , biocatalysis , oxidase test , alcohol oxidoreductase , organic chemistry , catalysis , reaction mechanism , biochemistry , oceanography , mutant , gene , geology , nad+ kinase
Abstract The substrate scope of the flavoprotein alditol oxidase (AldO) from Streptomyces coelicolor A3(2), recombinantly produced in Escherichia coli , was explored. While it has been established that AldO efficiently oxidizes alditols to D ‐aldoses, this study revealed that the enzyme is also active with a broad range of aliphatic and aromatic alcohols. Alcohols containing hydroxy groups at the C‐1 and C‐2 positions like 1,2,4‐butanetriol ( K m =170 mM, k cat =4.4 s −1 ), 1,2‐pentanediol ( K m =52 mM, k cat =0.85 s −1 ) and 1,2‐hexanediol ( K m =97 mM, k cat =2.0 s −1 ) were readily accepted by AldO. Furthermore, the enzyme was highly enantioselective for the oxidation of 1,2‐diols [e.g., for 1‐phenyl‐1,2‐ethanediol the ( R )‐enantiomer was preferred with an E ‐value of 74]. For several diols the oxidation products were determined by GC‐MS and NMR. Interestingly, for all tested 1,2‐diols the products were found to be the α‐hydroxy acids instead of the expected α‐hydroxy aldehydes. Incubation of ( R )‐1‐phenyl‐1,2‐ethanediol with 18 O‐labelled water (H 2 18 O) revealed that a second enzymatic oxidation step occurs via the hydrate product intermediate. The relaxed substrate specificity, excellent enantioselectivity, and independence of coenzymes make AldO an attractive enzyme for the preparation of optically pure 1,2‐diols and α‐hydroxy acids.