A unique class I polyhydroxyalkanoate synthase (PhaC) from Brevundimonas sp. KH11J01 exists as a functional trimer: A comparative study with PhaC from Cupriavidus necator H16.

Elsevier

Available online 6 May 2022

New BiotechnologyHighlights•

A type I PHA synthase from Brevundimonas sp. (BrPhaC) uniquely exists as trimer in absence of substrate

Enzymatic reaction of BrPhaC starts instantly without a lag-phase unlike many other PhaCs.

Duration of the lag-phase of PHA synthase from Cupriavidus necator H16 (RePhaC) was highly affected by temperature.

Optimal function of BrPhaC at ambient temperature is beneficial for energy efficient PHA production.

Abstract

Polyhydroxyalkanoates (PHAs) are natural biodegradable polyesters that are produced by numerous prokaryotic microorganisms primarily as a carbon- and energy reserve. The PhaC enzyme catalyzes the last step in the PHA biosynthesis pathway and synthesizes PHA polymers from hydroxyalkanoic acids. A type I PhaC from a PHA-producing marine bacterium Brevundimonas sp. KH11J01 (BrPhaC) was identified, produced recombinantly and characterized. Its properties were compared with its homolog from C. necator H16 (RePhaC). Unlike other PhaCs, it was found that BrPhaC is a lag-phase free enzyme organized as a trimer, even without the presence of a substrate. The enzymatic reaction is initiated instantly irrespective of temperature, in contrast to RePhaC in which the duration of the lag-phase was highly affected by temperature. At 10 oC BrPhaC was 40% active whereas RePhaC was barely active. The significance of using marine microorganisms, harboring cold-active PHA biosynthesis enzymes, for energy efficient PHA production, is also discussed briefly. The unique trimeric organization of BrPhaC challenges our understanding of the PhaC reaction mechanisms, which is mainly based on the crystal structures of the inactive forms of the enzyme.

AbbreviationsBrPhaC

PhaC from Brevundimonas sp.

RePhaC

PhaC from Cupriavidus necator H16 (in house construct)

CnPhaC

PhaC from C. necator H16 (from literature)

ChPhaC

Chromobacterium sp. USM2

CcPhaC

PhaC from Caulobacter crecentus

RsPhaC

Rhodovulum sulfidophilum

SEC

Size Exclusion Chromatography

DTNB

5,5'-dithiobis-2-nitrobenzoate

DSC

Differential Scanning Calorimetry

3HBCoA

3-Hydroxybutryl Coenzyme A

Keywords

Bioplastic

Polyhydroxyalkanoate

PHA synthase

protein oligomerization

Brevundimonas sp.

Cupriavidus necator H16

© 2022 The Author(s). Published by Elsevier B.V.

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