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Poly depolymerases

Fig. 1. The metabolic cycle for the synthesis and degradation of poly(3HB). (1) 3-ketothiolase (2) NADPH-dependent acetoacetyl-CoA reductase (3) poly(3HB) synthase (4) NADH-dependent acetoacetyl-CoA reductase (5), (6) enolases (7) depolymerase (8) d-(-)-3-hydroxybutyrate dehydrogenase (9) acetoacetyl-CoA synthetase (10) succinyl-CoA transferase (11) citrate synthase (12) see Sect. 3... Fig. 1. The metabolic cycle for the synthesis and degradation of poly(3HB). (1) 3-ketothiolase (2) NADPH-dependent acetoacetyl-CoA reductase (3) poly(3HB) synthase (4) NADH-dependent acetoacetyl-CoA reductase (5), (6) enolases (7) depolymerase (8) d-(-)-3-hydroxybutyrate dehydrogenase (9) acetoacetyl-CoA synthetase (10) succinyl-CoA transferase (11) citrate synthase (12) see Sect. 3...
Polyesters, such as microbially produced poly[(P)-3-hydroxybutyric acid] [poly(3HB)], other poly[(P)-hydroxyalkanoic acids] [poly(HA)] and related biosynthetic or chemosynthetic polyesters are a class of polymers that have potential applications as thermoplastic elastomers. In contrast to poly(ethylene) and similar polymers with saturated, non-functionalized carbon backbones, poly(HA) can be biodegraded to water, methane, and/or carbon dioxide. This review provides an overview of the microbiology, biochemistry and molecular biology of poly(HA) biodegradation. In particular, the properties of extracellular and intracellular poly(HA) hydrolyzing enzymes [poly(HA) depolymerases] are described. [Pg.289]

The poly(HA) depolymerases of the bacteria Alcaligenes faecalis (strains AE122 and Tl), Comamonas acidovorans, Comamonas testosteroni, Comamonas sp., Pseudomonas fluorescens, Pseudomonas lemoignei, Pseudomonas stutzeri, Ralstonia pickettii, Streptomyces exfoliatus, and of the fungi Paecilomyces lilaci-nus, Penicillium funiculosum, and Penicillium pinophilum have been purified and characterized (for details see Table 1). Poly(HA) depolymerases share several characteristics ... [Pg.293]

Most poly(HA) depolymerases are inhibited by reducing agents, e.g., dithio-erythritol (DTT), which indicates the presence of essential disulfide bonds, and by serine hydrolase inhibitors such as diisopropyl-fluoryl phosphate (DFP) or acylsulfonyl derivates. The latter compounds covalently bind to the active site serine of serine hydrolases and irreversibly inhibit enzyme activity [48]. [Pg.293]

Table 1. Overview on poly(HA)-degrading microorganisms and biochemical characterization of purified poly(HA)-depolymerases... [Pg.294]

Poly(HA)SCL depolymerase with high poly(3HV) depolymerase activity... [Pg.295]

Relationship between poly(3HB) depolymerase synthesis and uptake of succinate 88 Depolymerase with acidic pH optimum 183... [Pg.295]

Poly(HAMCL) depolymerases of Gram-negative aerobic bacteria ... [Pg.296]

Poly(3HB) depolymerase with cadherin-like linker domain 57... [Pg.297]

Poly(3HO) depolymerase that does not hydrolyze poly(3HB) 23... [Pg.297]

In rec. E. coli processing of poly(3HO) depolymerase differs from wild type 67... [Pg.297]

Poly(HA) depolymerases - as far as it has been tested - do not bind to anion exchangers such as DEAE (at neutral pH) but have a pronounced affinity to hydrophobic materials. Therefore, many purification protocols include hydrophobic interaction chromatography. [Pg.298]

All purified poly(HA) depolymerases are specific for either poly(HASCL) or poly(HAMCL). Even a poly(3HB) depolymerase of S. exfoliatus K10, a strain that degrades both poly(3HB) and poly(3HO), is specific for poly(HASCL) [49]) indicating at least one additional depolymerase with specificity for poly(HAMCL) in S. exfoliatus. Experiments with copolymers consisting of 3-hydroxybutyrate and 3-hydroxyhexanoate and A.faecalis T1 poly(3HB) depolymerase are in agreement with the results obtained with poly(HASCL) and poly(HAMCL) the depolymerase was not able to hydrolyze ester bonds between two 3HAMCL monomers and between 3-hydroxybutyrate and 3-hydroxyhexanoate [50]. [Pg.298]

Molecular Biology and Functional Analysis of Poly(HAsa) Depolymerases... [Pg.298]

Table 2. Characteristics of bacterial poly(3HA) depolymerase genes... [Pg.299]

All poly(HASCL) depolymerase proteins have a composite domain structure (Fig. 2) and consist of ... [Pg.301]

Poly(HASCL) depolymerases are able to bind to poly(3HB)-granules. This ability is specific because poly(3HB) depolymerases do not bind to chitin or to (crystalline) cellulose [56,57]. The poly(3HB)-binding ability is lost in truncated proteins which lack the C-terminal domain of about 60 amino acids, and these modified enzymes do not hydrolyze poly(3HB). However, the catalytic domain is unaffected since the activity with water-soluble oligomers of 3-hy-droxybutyrate or with artificial water-soluble substrates such as p-nitrophenyl-esters is unaffected [55, 56, 58, 59]. Obviously, the C-terminal domain of poly(3HB) depolymerases is responsible and sufficient for poly(3HB)-binding [poly(3HB)-binding domain]. These results are in agreement ... [Pg.301]

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