Rubber oxygenases

Abstract

Natural rubber (NR), poly(cis-1,4-isoprene), is used in an industrial scale for more than 100 years. Most of the NR-derived materials are released to the environment as waste or by abrasion of small particles from our tires. Furthermore, compounds with isoprene units in their molecular structures are part of many biomolecules such as terpenoids and carotenoids. Therefore, it is not surprising that NR-degrading bacteria are widespread in nature. NR has one carbon-carbon double bond per isoprene unit and this functional group is the primary target of NR-cleaving enzymes, so-called rubber oxygenases. Rubber oxygenases are secreted by rubber-degrading bacteria to initiate the break-down of the polymer and to use the generated cleavage products as a carbon source. Three main types of rubber oxygenases have been described so far. One is rubber oxygenase RoxA that was first isolated from Xanthomonas sp. 35Y but was later also identified in other Gram-negative rubber-degrading species. The second type of rubber oxygenase is the latex clearing protein (Lcp) that has been regularly found in Gram-positive rubber degraders. Recently, a third type of rubber oxygenase (RoxB) with distant relationship to RoxAs was identified in Gram-negative bacteria. All rubber oxygenases described so far are haem-containing enzymes and oxidatively cleave polyisoprene to low molecular weight oligoisoprenoids with terminal CHO and CO–CH3 functions between a variable number of intact isoprene units, depending on the type of rubber oxygenase. This contribution summarises the properties of RoxAs, RoxBs and Lcps.

Microbial biosynthesis and in vivo depolymerization of intracellular medium‐chain‐length poly‐3‐hydroxyalkanoates as potential route to platform chemicals

“…Mcl-PHA C 6 -HHx C 8 -HO C 10 -HD C 12 Material T2). Then, different molar concentrations of Tris-HCl buffer in the range from 0.025 to 0.5 M were investigated at the optimum incubation temperature 30 • C (Supplemental Material T3).…”

“…Mcl-PHA C 6 -HHx C 8 -HO C 10 -HD C 12 to other factors such as temperature. This also opens up the possibility of adopting the aforementioned system for chiral molecules production in a cell-free biology process [51].…”

“…PHA synthesized from renewable resources are considered attractive substitutes to petrochemical-based plastics due to their biodegradability, sustainability, and nontoxicity [2,3]. Furthermore, PHA have broad potential applications owing to properties such as excellent processability, hydrophobicity, biocompatibility, resorbability, piezoelectricity, and diverse mechanical properties [4][5][6][7][8]. Short-chain-length PHA (scl-PHA) with 3-5 carbon atom length and medium-chain-length PHA (mcl-PHA) with 6-14 carbon atom length are classified based on their monomer identity and numbers of monomer carbon atoms [9,10].…”

First report of cis-1,4-polyisoprene degradation by Gordonia paraffinivorans

“…The Gram-negative bacterium S. cummioxidans 35Y lacks the lcp, but is able to degrade rubber due to the action of the Rubber oxygenase A (RoxA) [10]. Myxococcus fulvus, Haliangium ochraceum, Corallococcus coralloides, all gamma-proteobacteria, and also R. gummiphilus NS21 have the gene roxA [28,29]. Recent studies demonstrated that RoxA from R. gummiphilus is able to cleave polyisoprene to the C15 oligoisoprenoid [28].…”

“…Recently, a novel type of rubber oxygenase was reported in S. cummioxidans 35Y (RoxB) [30] and R. gummiphilus NS21 (LatA) [11,31]. Comparisons of the amino acid sequence and other properties showed RoxB and LatA are homologues, but RoxA is not a homologue of RoxB/LatA [28][29][30]. Two species of Gordonia (G. westfalica and G. polyisoprenivorans) have been associated to rubber degradation; both have the Lcp and are able to use this substrate as sole carbon source [12,13].…”