Affiliation:
1. Department of Bioengineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 940-2188
2. Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
Abstract
ABSTRACT
A lignin-related biphenyl compound, 5,5′-dehydrodivanillate (DDVA), is degraded to 5-carboxyvanillate (5CVA) by the enzyme reactions catalyzed by DDVA
O
-demethylase (LigX),
meta
-cleavage oxygenase (LigZ), and
meta
-cleavage compound hydrolase (LigY) in
Sphingomonas paucimobilis
SYK-6. 5CVA is then transformed to vanillate by a nonoxidative 5CVA decarboxylase and is further degraded through the protocatechuate 4,5-cleavage pathway. A 5CVA decarboxylase gene,
ligW
, was isolated from SYK-6 (X. Peng, E. Masai, H. Kitayama, K. Harada, Y, Katayama, and M. Fukuda, Appl. Environ. Microbiol.
68:
4407-4415, 2002). However, disruption of
ligW
slightly affected the 5CVA decarboxylase activity and the growth rate on DDVA of the mutant, suggesting the presence of an alternative 5CVA decarboxylase gene. Here we isolated a second 5CVA decarboxylase gene,
ligW2
, which consists of a 1,050-bp open reading frame encoding a polypeptide with a molecular mass of 39,379 Da. The deduced amino acid sequence encoded by
ligW2
exhibits 37% identity with the sequence encoded by
ligW
. Based on a gas chromatography-mass spectrometry analysis of the reaction product from 5CVA catalyzed by LigW2 in the presence of deuterium oxide, LigW2 was indicated to be a nonoxidative decarboxylase of 5CVA, like LigW. After disruption of
ligW2
, both the growth rate on DDVA and the 5CVA decarboxylase activity of the mutant were decreased to approximately 30% of the wild-type levels. The
ligW ligW2
double mutant lost both the ability to grow on DDVA and the 5CVA decarboxylase activity. These results indicate that both
ligW
and
ligW2
contribute to 5CVA degradation, although
ligW2
plays the more important role in the growth of SYK-6 cells on DDVA.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
44 articles.
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