Thiolysis of poly(3-hydroxybutyrate) — A novel biochemical reaction

An enzyme involved in the degradation of poly(3-hydroxybutyrate) (PHB), PhaZa1 from Ralstonia eutropha H16, catalyzes the thiolysis of PHB with coenzyme A. The properties of this novel reaction were investigated in vitro. The active center’s cysteine residue was point-mutated to prepare C183S and C183A. The wild type and the two mutants were compared in terms of hydrolytic and thiolytic activity. C183S was as active as the wild type in the hydrolysis, but less active in the thiolysis, of PHB. The cysteine residue was important for the thiolysis of PHB, which may be why it has been conserved in almost all PhaZa1 homologs in various bacteria.Key words: PHB, thiolysis, PHB depolymerase

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