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Journal of Bacteriology, August 2005, p. 5067-5074, Vol. 187, No. 15
0021-9193/05/$08.00+0     doi:10.1128/JB.187.15.5067-5074.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Characterization of the Gallate Dioxygenase Gene: Three Distinct Ring Cleavage Dioxygenases Are Involved in Syringate Degradation by Sphingomonas paucimobilis SYK-6{dagger}

Daisuke Kasai,1 Eiji Masai,1* Keisuke Miyauchi,1 Yoshihiro Katayama,2 and Masao Fukuda1

Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188,1 Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan2

Received 22 April 2005/ Accepted 29 April 2005

Sphingomonas paucimobilis SYK-6 converts vanillate and syringate to protocatechuate (PCA) and 3-O-methylgallate (3MGA) in reactions with the tetrahydrofolate-dependent O-demethylases LigM and DesA, respectively. PCA is further degraded via the PCA 4,5-cleavage pathway, whereas 3MGA is metabolized via three distinct pathways in which PCA 4,5-dioxygenase (LigAB), 3MGA 3,4-dioxygenase (DesZ), and 3MGA O-demethylase (LigM) are involved. In the 3MGA O-demethylation pathway, LigM converts 3MGA to gallate, and the resulting gallate appears to be degraded by a dioxygenase other than LigAB or DesZ. Here, we isolated the gallate dioxygenase gene, desB, which encodes a 418-amino-acid protein with a molecular mass of 46,843 Da. The amino acid sequences of the N-terminal region (residues 1 to 285) and the C-terminal region (residues 286 to 418) of DesB exhibited ca. 40% and 27% identity with the sequences of the PCA 4,5-dioxygenase ß and {alpha} subunits, respectively. DesB produced in Escherichia coli was purified and was estimated to be a homodimer (86 kDa). DesB specifically attacked gallate to generate 4-oxalomesaconate as the reaction product. The Km for gallate and the Vmax were determined to be 66.9 ± 9.3 µM and 42.7 ± 2.4 U/mg, respectively. On the basis of the analysis of various SYK-6 mutants lacking the genes involved in syringate degradation, we concluded that (i) all of the three-ring cleavage dioxygenases are involved in syringate catabolism, (ii) the pathway involving LigM and DesB plays an especially important role in the growth of SYK-6 on syringate, and (iii) DesB and LigAB are involved in gallate degradation.

* Corresponding author. Mailing address: Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan. Phone: 81-258-47-9428. Fax: 81-258-47-9450. E-mail: emasai{at}vos.nagaokaut.ac.jp.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, August 2005, p. 5067-5074, Vol. 187, No. 15
0021-9193/05/$08.00+0     doi:10.1128/JB.187.15.5067-5074.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.





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