Two different pathways are involved in the beta-oxidation of n-alkanoic and n-phenylalkanoic acids in Pseudomonas putida U: genetic studies and biotechnological applications.
In Pseudomonas putida U, the degradation of n-alkanoic and n-phenylalkanoic acids is carried out by two sets of beta-oxidation enzymes (betaI and betaII). Whereas the first one (called betaI) is constitutive and catalyses the degradation of n-alkanoic and n-phenylalkanoic acids very efficiently, the other one (betaII), which is only expressed when some of the genes encoding betaI enzymes are mutated, catabolizes n-phenylalkanoates (n > 4) much more slowly. Genetic studies revealed that disruption or deletion of some of the betaI genes handicaps the growth of P. putida U in media containing n-alkanoic or n-phenylalkanoic acids with an acyl moiety longer than C4. However, all these mutants regained their ability to grow in media containing n-alkanoates as a result of the induction of betaII, but they were still unable to catabolize n-phenylalkanoates completely, as the betaI-FadBA enzymes are essential for the beta-oxidation of certain n-phenylalkanoyl-CoA derivatives when they reach a critical size. Owing to the existence of the betaII system, mutants lacking betaIfadB/A are able to synthesize new poly 3-OH-n-alkanoates (PHAs) and poly 3-OH-n-phenylalkanoates (PHPhAs) efficiently. However, they are unable to degrade these polymers, becoming bioplastic overproducer mutants. The genetic and biochemical importance of these results is reported and discussed.
Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de León, 24007 León, Spain.
E R
ER
Olivera
D
D
Carnicero
B
B
García
B
B
Miñambres
M A
MA
Moreno
L
L
Cañedo
C C
CC
Dirusso
G
G
Naharro
J M
JM
Luengo
D000144:Acids, Acyclic / Q000378:metabolism*; D000222:Adaptation, Physiological; D000473:Alkanes / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001483:Base Sequence; D001709:Biotechnology; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D005227:Fatty Acids / Q000378:metabolism*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis; D010084:Oxidation-Reduction; D016958:Pseudomonas putida / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology
D000144:Acids, Acyclic; D000473:Alkanes; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D005227:Fatty Acids; D009097:Multienzyme Complexes; D003066:Coenzyme A Ligases; C085934:acyl-coenzyme A synthetase, E coli