Affiliation:
1. Institut für Mikrobiologie, Universität Stuttgart
2. Institut für Lebensmittelchemie, Universität Hohenheim, Stuttgart, Germany
Abstract
ABSTRACT
Oxidative cleavage of poly(
cis
-1,4-isoprene) by rubber oxygenase RoxA purified from
Xanthomonas
sp. was investigated in the presence of different combinations of
16
O
2
,
18
O
2
, H
2
16
O, and H
2
18
O. 12-Oxo-4,8-dimethyl-trideca-4,8-diene-1-al (ODTD;
m
/
z
236) was the main cleavage product in the absence of
18
O-compounds. Incorporation of one
18
O atom in ODTD was found if the cleavage reaction was performed in the presence of
18
O
2
and H
2
16
O. Incubation of poly(
cis
-1,4-isoprene) (with RoxA) or of isolated unlabeled ODTD (without RoxA) with H
2
18
O in the presence of
16
O
2
indicated that the carbonyl oxygen atoms of ODTD significantly exchanged with oxygen atoms derived from water. The isotope exchange was avoided by simultaneous enzymatic reduction of both carbonyl functions of ODTD to the corresponding dialcohol (12-hydroxy-4,8-dimethyl-trideca-4,8-diene-1-ol (HDTD;
m
/
z
240) during RoxA-mediated in vitro cleavage of poly(
cis
-1,4-isoprene). In the presence of
18
O
2
, H
2
16
O, and alcohol dehydrogenase/NADH, incorporation of two atoms of
18
O into the reduced metabolite HDTD was found (
m
/
z
244), revealing that RoxA cleaves rubber by a dioxygenase mechanism. Based on the labeling results and the presence of two hemes in RoxA, a model of the enzymatic cleavage mechanism of poly(
cis
-1,4-isoprene) is proposed.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
66 articles.
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