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Polymers 2018, 10(8), 910;

Role of PhaC Type I and Type II Enzymes during PHA Biosynthesis

Department of Biological and Environmental Science and Technologies, University of Salento, Ecotekne, 73100 Lecce, Italy
CNR, Agrofood Department, Institute of Sciences of Food Productions (ISPA-CNR), 73100 Lecce, Italy
Author to whom correspondence should be addressed.
Received: 26 July 2018 / Revised: 9 August 2018 / Accepted: 9 August 2018 / Published: 13 August 2018
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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PHA synthases (PhaC) are grouped into four classes based on the kinetics and mechanisms of reaction. The grouping of PhaC enzymes into four classes is dependent on substrate specificity, according to the preference in forming short-chain-length (scl) or medium-chain-length (mcl) polymers: Class I, Class III and Class IV produce scl-PHAs depending on propionate, butyrate, valerate and hexanoate precursors, while Class II PhaC synthesize mcl-PHAs based on the alkane (C6 to C14) precursors. PHA synthases of Class I, in particular PhaCCs from Chromobacterium USM2 and PhaCCn/RePhaC1 from Cupriavidus necator/Ralstonia eutropha, have been analysed and the crystal structures of the C-domains have been determined. PhaCCn/RePhaC1 was also studied by X-ray absorption fine-structure (XAFS) analysis. Models have been proposed for dimerization, catalysis mechanism, substrate recognition and affinity, product formation, and product egress route. The assays based on amino acid substitution by mutagenesis have been useful to validate the hypothesis on the role of amino acids in catalysis and in accommodation of bulky substrates, and for the synthesis of PHB copolymers and medium-chain-length PHA polymers with optimized chemical properties. View Full-Text
Keywords: PhaC synthase; classification; dimerization; substrate binding; exit cavity; C3–C14 alkanes; polymer composition PhaC synthase; classification; dimerization; substrate binding; exit cavity; C3–C14 alkanes; polymer composition

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Mezzolla, V.; D’Urso, O.F.; Poltronieri, P. Role of PhaC Type I and Type II Enzymes during PHA Biosynthesis. Polymers 2018, 10, 910.

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