RESUMO
A single-copy gene resembling the gene for the delta9 acyl-lipid desaturase (desC) was cloned from the thermophilic cyanobacterium Synechococcus vulcanus. Expression of desC in Escherichia coli confirmed that it encodes the delta9 desaturase. The nucleotide sequence of the desC was characterized by high G+C content that is typical of the sequences of thermophilic bacteria. The deduced amino acid sequence exhibited low Cys content and high Arg/Lys ratio that are the attributes of thermostable enzymes. A low level of the desC mRNA was detected in the cells grown at 55 degrees C, the optimum growth temperature for S. vulcanus. About a 10-fold increase was observed in the levels of the transcript and the protein during the shift in temperature from 55 to 45 degrees C. At 35 degrees C the amount of the desC mRNA and of the enzyme accumulated in the cells, was 3 to 4 times smaller than at 45 degrees C. At both temperatures, however, lipids were desaturated at similar rates. These results suggest that in S. vulcanus the conversion of stearic acid into oleic acid may be controlled not only by the de novo synthesis of the delta9 desaturase but, possibly, by the activation of the pre-existing enzyme.
Assuntos
Cianobactérias/enzimologia , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Dessaturases/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Cianobactérias/genética , Escherichia coli/genética , Ácidos Graxos/química , Ácidos Graxos/metabolismo , Regulação Bacteriana da Expressão Gênica , Dados de Sequência Molecular , RNA Mensageiro/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Homologia de Sequência de Aminoácidos , Estearoil-CoA Dessaturase , TemperaturaRESUMO
Pseudomonas putida BS202 degrades naphthalene via a plasmid-encoded catabolic pathway. The nucleotide sequence of the nahC gene encoding one of this pathway enzymes, 1,2-dihydroxynaphthalene dioxygenase, has been determined. Analysis of nucleotide sequence of its flanking regions identified partially the nahF and putative nahQ genes. Comparison of these three genes with corresponding ones in the NAH7 plasmid and DOX operon showed a high degree of homology.