title: First-order kinetics analysis of monomer composition dependent polyhydroxyalkanoic acid degradation in Pseudomonas spp.
abstract: The intracellular degradation of polyhydroxyalkanoic acid (PHA) in pseudomonads was investigated by first-order kinetics analysis using the initial rate method. One type of PHA was accumulated in five Pseudomonas spp., P. oleovorans, P. aeruginosa, P. fluorescens, P. citronellolis, and P. putida, by growing them on octanoic acid. The monomer compositions of the five PHA were not significantly different from one another: 85-90 mol % 3-hydroxyoctanoic acid (3HO), 7-12 mol % 3-hydorxycaproic acid (3HC), and 3-6 mol % 3-hydroxydecanoic acid (3HD). The first-order degradation rate constants (k(1)) for the octanoate-derived PHA (designated P(3HO)) in the five species were in a similar range between 0.060 and 0.088 h(-1). This may indicate the similar specificities of the five intracellular depolymerases. In addition, the similar k(1) among the different species may correlate with the high degree of amino acid sequence identities (over 85%) among the intracellular PHA depolymerase phaZ genes. Six other chemically different types of PHA were accumulated in P. putida from n-nonanoic acid, n-decanoic acid, 5-phenyvaleric acid, or 11-phenoxyundecanoic acid as a single or a mixed carbon source. The calculated k(1) values were characteristic to each PHA, reflecting their chemical structures. In comparison with P(3HO), an increase in the levels of the two minor monomers 3HC and 3HD as in P(21 mol % 3HC-co-56 mol % 3HO-co-23 mol % 3HD) significantly slowed the rate of intracellular degradation. From the comparison of k(1) values, it is suggested that the P. putida intracellular depolymerase is most active against P(3HO).
authors.affiliation: Biomaterials Science Laboratory, Division of Life Science at the College of Natural Sciences, Gyeongsang National University, Chinju 660-701, Korea.
authors.forename: Mun Hwan
authors.initials: MH
authors.lastname: Choi
authors.forename: Jong Kook
authors.initials: JK
authors.lastname: Rho
authors.forename: Ho-Joo
authors.initials: HJ
authors.lastname: Lee
authors.forename: Jae Jun
authors.initials: JJ
authors.lastname: Song
authors.forename: Sung Chul
authors.initials: SC
authors.lastname: Yoon
authors.forename: Sang Yeol
authors.initials: SY
authors.lastname: Lee
mesh_terms: D000143:Acids / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D016958:Pseudomonas putida / Q000378:metabolism*
chemical_list: D000143:Acids