title: Synergistic effects of Glu130Asp substitution in the type II polyhydroxyalkanoate (PHA) synthase: enhancement of PHA production and alteration of polymer molecular weight.
abstract: In vitro evolution of the polyhydroxyalkanoate (PHA) synthase gene from Pseudomonas sp. 61-3 (phaC1(Ps)) has been performed to generate highly active enzymes. In this study, a positive mutant of PHA synthase, Glu130Asp (E130D), was characterized in detail in vivo and in vitro. Recombinant Escherichia coli strain JM109 harboring the E130D mutant gene accumulated 10-fold higher (1.0 wt %) poly(3-hydroxybutyrate) [P(3HB)] from glucose, compared to recombinant E. coli harboring the wild-type PHA synthase gene (0.1 wt %). Recombinant E. coli strain LS5218 harboring the E130D PHA synthase gene grown on dodecanoate produced more poly(3HB-co-3-hydroxyalkanoate) [P(3HB-co-3HA)] (20 wt %) copolymer than an LS5218 strain harboring the wild-type PHA synthase gene (13 wt %). The E130D mutation also resulted in the production of copolymer with a slight increase in 3HB composition, compared to copolymer produced by the wild-type PHA synthase. In vitro enzyme activities of the E130D PHA synthase toward various 3-hydroxyacyl-CoAs (4-10 carbons in length) were all higher than those of the wild-type enzyme. The combination of the E130D mutation with other beneficial mutations, such as Ser325Thr and Gln481Lys, exhibited a synergistic effect on in vivo PHA production and in vitro enzyme activity. Interestingly, gel-permeation chromatography analysis revealed that the E130D mutation also had a synergistic effect on the molecular weight of polymers produced in vivo.
authors.affiliation: Polymer Chemistry Laboratory, RIKEN Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan. mken@riken.jp
authors.forename: Ken'ichiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Kazuma
authors.initials: K
authors.lastname: Takase
authors.forename: Emi
authors.initials: E
authors.lastname: Aoki
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Doi
authors.forename: Seiichi
authors.initials: S
authors.lastname: Taguchi
mesh_terms: D000217:Acyltransferases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001216:Asparagine / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005973:Glutamine / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D011108:Polymers / Q000737:chemistry*; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D013329:Structure-Activity Relationship
chemical_list: D011108:Polymers; D011994:Recombinant Proteins; D005973:Glutamine; D001216:Asparagine; D000217:Acyltransferases; C077225:poly(3-hydroxyalkanoic acid) synthase