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Polyhydroxyalkanoates (PHAs)

Polyhydroxyalkanoates (PHAs) are synthesized by a wide variety of bacteria as storage and reserve materials. PHAs are linked by ester bonds and today >150 different types of monomers can be combined resulting in a wide range of different types of bioplastics (Verlinden, 2007, Jendrossek, 2013). PHAs are synthesized from 3-hydroxy fatty acid monomers. During the synthesis the carboxyl group of one monomer forms an ester bond with the hydroxyl group of the next monomer. While these polymers are inpriciple based on natural resources they can be built from fossil fuels; and in fact more than half of the globally proiduced poylmers are not based on renewable resources.

Since PHAs are 'natural polymers', degradation is possible. However, some PHA variants are not biodegradable. The biodegradation of PHA has been observed in many different bacteria and fungi from marine and terrestrial sites (Jendrossek, 2002, Suzuki, 2021, Viljakianen, 2021) . The enzymes involved are either secreted extracellular PHA depolymerases (e-PHA depolymerases) or internal PHA (i-PHA) depolymerases. The known depolymerases are carboxyesterases (EC / EC and the best characterized enzymes are derived from Cuprivadus nector (Ralstonia eutropha) and Paucimonas lemoignei. Both are bacterial model organisms for PHA (PHB) metabolism. Measurements of enzyme activities are technically difficult (Jendrossek, 2007). Notably, only a few enzymes were characterized in detail. The best-studied and verified enzymes are listed below:

Microbial host/enzyme/genelocation/commentReferenceGenBank/ UniProtPDB entryNCBI BLAST
Pseudomonadota (synonym with Proteobacteria)
Cuprivadus necator ATC17699, DSM428 (Ralstonia eutropha, Wautersia eutropha), phaZ 1-7 internalBrigham,2012
-Phaz1internalHandrick, 2000, Saegusa, 2001Q0KCI0 Q0KCI0
-PhaZ2internalYork, 2003Q0K7T2 Q0K7T2
-PhaZ3internalYork, 2003, Brigham,2012Q0K4D5 Q0K4D5
-PhaZ4internalBrigham,2012Q7WXF6 Q7WXF6
-PhaZ5internalBrigham,2012Q0K2G9 Q0K2G9
-PhaZ6 (PhaZd1)externalAbe, 2005; Sznajder, 2014 Q0JZG9 Q0JZG9
-PhaZ7 (PhaZd2)externalSznajder, 2014 Q0JYJ1 Q0JYJ1
-PhaY1 (PhaZ2)acts on oligomersBrigham,2012Q0K9H3 Q0K9H3
-PhaY2acts on oligomersBrigham,2012Q0KBZ6 Q0KBZ6
Alcaligenes faecalis, PhaZAfa Kasuya, 1999P94146 P94146
Paucimonas lemoignei, PhaZ7 Jendrossek, 2013Q939Q94BTV, and variantsQ939Q9
Paucimonas lemoignei, PhaZ5 Braaz, 2002Q51871 Q51871
Pseudomonas stutzeri, PhaZst Ohura, 1999, Kasuya 1999O82950 O82950
Commamonas acidivorans, YM1609, PhaZCac Kasuya, 1997; Kasuya 1999A0A080NJE8 KFJ10595.1
Pseudomonas putida KT2442, PhaZ Eugenio, 2007AE015451
Talaromyces (Penicilium) funiculosus Miyazaki, 2000; Brucato, 1991B2NHN22D81, D280BAG32152.1

pha.txt · Last modified: 2024/03/24 11:09 by