Process | Proteins | Organism | Features | Refs. | |
---|---|---|---|---|---|
PHA synthesis | PhaEC | Haloarchaea | Haloarcula marismortui | Class III type; constitutes the active PHA synthase; co-transcription; constitutive expression; conserved lipase box-like sequence, amino acid triad (Cys-Asp-His), conserved motif of class III PHA and longer C-terminal sequence | [104] |
Haloarcula hispanica | [104] | ||||
Haloferax mediterranei | [41] | ||||
Halogranum amylolyticum TNN58 | Conserved lipase box-like sequence and catalytic triad residues; 64% and 62% identity with PhaE and PhaC from Hfx. mediterranei | [46] | |||
PhaC1 | Haloferax mediterranei | Lipase box-like sequence, conserved motif of class III PHA synthase and longer C-terminal sequence | [105] | ||
PhaC2 | Ala instead of the last Gly in lipase box-like sequence; conserved motif not strongly conserved; longer C-terminal sequence missing, without PhaC function | [105] | |||
PhaC3 | Lipase box-like sequence, conserved motif of class III PHA synthase and longer C-terminal sequence | [105] | |||
PhaC | Halorubrum lacusprofundi | High abundance at low temperature; C-terminal has 47% identity with the C-terminal of Haloferax mediterranei PhaC | [38] | ||
PhaC | Halophilic bacteria | Halomonas elongata DSM2581 | Two candidate genes; phaC1 is functional; unique serine instead of the first glycine in lipase box-like sequence; PhaC1 has affinity towards both 3HB and 3HV monomers | [101] | |
Halomonas sp. O-1 | |||||
Halomonas sp. R5-57 | Three candidate encoding genes; the third PhaC is truncated | [106] | |||
Yangia sp. CCB-MM3 | Class I type; two candidate encoding genes | [107] | |||
PhaC1 | Halomonas bluephagenesis TD01 | Conserved catalytic triad (Cys-Asp-His) and the conserved lipase box-like; Ser instead of first Gly in lipase box-like sequence | [52] | ||
PhaC2 | Conserved catalytic triad (Cys-Asp-His) and the conserved lipase box-like; longer C-terminus; shorter N-terminus; Ala instead of the last Gly in lipase box-like sequence | ||||
BktB | Haloarchaea | Haloferax mediterranei | Two subunits, α and β; α is the catalytic subunit and the catalytic residues are Ser-His-His; β subunit comprises of oligo-sachharide binding domain | [109] | |
PhaA | |||||
PhaA | Halophilic bacteria | Halomonas elongata BK-AG18 | One subunit, catalytic residues are Cys-His-Cys | [112] | |
PhaB | Haloarchaea | Haloferax mediterranei | NADPH-dependent; two candidate encoding genes, phaB1 and phaB2; PhaB1 and PhaB2 responsible for 3HB-CoA and 3HV-CoA formation | [113] | |
Haloarcula hispanica | NADPH-dependent; only FabG1 responsible for PHA synthesis | [114] | |||
Halophilic bacteria | Halomonas bluephagenesis TD01 | NADH-dependent | [115] | ||
PHA regulation | PhaP | Haloarchaea | Haloferax mediterranei | Consists of conserved amino acids and aspartate/glutamate rich regions in C-terminal; lysine acetylated | |
Halophilic bacteria | Halomonas bluephagenesis TD01 | Three candidate encoding genes; only PhaP1 responsible for the amount and size of PHA granules | [116] | ||
PhaR | Haloarchaea | Haloferax mediterranei | Consists of AbrB (antibiotic resistance protein B)—like domain; regulates function of PhaP | [118] | |
Halophilic bacteria | Halomonas bluephagenesis TD01 | Regulates PHA synthesis; amphiphilic property; strong and robust emulsifier | |||
PHA degradation | PhaZh1 | Haloarchaea | Haloferax mediterranei | Palatin-like protein; Contains classical lipase box-like | [121] |
BdhA | Encoding gene located upstream of phaZh1; hydrolyses 3HB monomers generated by PhaZ1 from natural PHA granules | [121] | |||
PhaJ | Dehydrates 3-hydroxyacyl-CoA to enoyl-CoA | [100] | |||
PhaZ1 | Halophilic bacteria | Halomonas bluephagenesis TD01 | Lacks signal peptide, intracellular depolymerase | [52] | |
PhaZ2 | |||||
PhaZ3 | Signal peptide present, extracellular depolymerase |