Stereoinversion via Alcohol Dehydrogenases Enables Complete Catabolism of β-1-Type Lignin-Derived Aromatic Isomers
- Nagaoka University of Technology (Japan)
- Forestry and Forest Products Research Institute (Japan)
- National Renewable Energy Laboratory (NREL), Golden, CO (United States). Renewable Resources and Enabling Science Center
Sphingobium sp. strain SYK-6 is an efficient aromatic catabolic bacterium that can consume all four stereoisomers of 1,2-diguaiacylpropane-1,3-diol (DGPD), which is a ring-opened β-1-type dimer. Recently, LdpA-mediated catabolism of erythro-DGPD was reported in SYK-6, but the catabolic pathway for threo-DGPD was as yet unknown. Here, in this study, we elucidated the catabolism of threo-DGPD, which proceeds through conversion to erythro-DGPD. When threo-DGPD was incubated with SYK-6, the Cα hydroxy groups of threo-DGPD (DGPD I and II) were initially oxidized to produce the Cα carbonyl form (DGPD-keto I and II). This initial oxidation step is catalyzed by Cα-dehydrogenases, which belong to the short-chain dehydrogenase/reductase (SDR) family and are involved in the catabolism of β-O-4-type dimers. Analysis of seven candidate genes revealed that NAD+-dependent LigD and LigL are mainly involved in the conversion of DGPD I and II, respectively. Next, we found that DGPD-keto I and II were reduced to erythro-DGPD (DGPD III and IV) in the presence of NADPH. Genes involved in this reduction were sought from Cα-dehydrogenase and ldpA-neighboring SDR genes. The gene products of SLG_12690 (ldpC) and SLG_12640 (ldpB) catalyzed the NADPH-dependent conversion of DGPD-keto I to DGPD III and DGPD-keto II to DGPD IV, respectively. Mutational analysis further indicated that ldpC and ldpB are predominantly involved in the reduction of DGPD-keto. Together, these results demonstrate that SYK-6 harbors a comprehensive catabolic enzyme system to utilize all four β-1-type stereoisomers through successive oxidation and reduction reactions of the Cα hydroxy group of threo-DGPD with a net stereoinversion using multiple dehydrogenases.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Bioenergy Technologies Office (BETO); USDOE Office of Science (SC), Biological and Environmental Research (BER)
- Grant/Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1984226
- Report Number(s):
- NREL/JA-2A00-86481; MainId:87254; UUID:74935807-3d60-4ae4-b133-fbb1bc3446f6; MainAdminID:69711
- Journal Information:
- Applied and Environmental Microbiology, Journal Name: Applied and Environmental Microbiology Journal Issue: 6 Vol. 89; ISSN 0099-2240
- Publisher:
- American Society for MicrobiologyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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