title: Phasin proteins activate Aeromonas caviae polyhydroxyalkanoate (PHA) synthase but not Ralstonia eutropha PHA synthase.
abstract: In this study, we performed in vitro and in vivo activity assays of polyhydroxyalkanoate (PHA) synthases (PhaCs) in the presence of phasin proteins (PhaPs), which revealed that PhaPs are activators of PhaC derived from Aeromonas caviae (PhaCAc). In in vitro assays, among the three PhaCs tested, PhaCAc was significantly activated when PhaPs were added at the beginning of polymerization (prepolymerization PhaCAc), whereas the prepolymerization PhaCRe (derived from Ralstonia eutropha) and PhaCDa (Delftia acidovorans) showed reduced activity with PhaPs. The PhaP-activated PhaCAc showed a slight shift of substrate preference toward 3-hydroxyhexanoyl-CoA (C6). PhaPAc also activated PhaCAc when it was added during polymerization (polymer-elongating PhaCAc), while this effect was not observed for PhaCRe. In an in vivo assay using Escherichia coli TOP10 as the host strain, the effect of PhaPAc expression on PHA synthesis by PhaCAc or PhaCRe was examined. As PhaPAc expression increased, PHA production was increased by up to 2.3-fold in the PhaCAc-expressing strain, whereas it was slightly increased in the PhaCRe-expressing strain. Taken together, this study provides evidence that PhaPs function as activators for PhaCAc both in vitro and in vivo but do not activate PhaCRe. This activating effect may be attributed to the new role of PhaPs in the polymerization reaction by PhaCAc.
authors.affiliation: Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Ushimaru
authors.forename: Yoko
authors.initials: Y
authors.lastname: Motoda
authors.forename: Keiji
authors.initials: K
authors.lastname: Numata
authors.forename: Takeharu
authors.initials: T
authors.lastname: Tsuge
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000333:Aeromonas / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020118:Cupriavidus necator / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D037121:Plant Lectins / Q000737:chemistry / Q000378:metabolism*; D054813:Polyhydroxyalkanoates / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D020536:Enzyme Activators; D037121:Plant Lectins; D054813:Polyhydroxyalkanoates; C008825:phasin; D000217:Acyltransferases; C077225:poly(3-hydroxyalkanoic acid) synthase