Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.10.3.2 (laccase)
 4,656 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Marinomonas mediterranea is a melanogenic marine bacterium expressing a multifunctional polyphenol oxidase (PPO) able to oxidize substrates characteristic for laccases and tyrosinases, as well as produce a classical tyrosinase. A new and quick method has been developed for screening laccase activity in culture plates to detect mutants differentially affected in this PPO activity. Transposon mutagenesis has been applied for the first time to M. mediterranea by using different minitransposons loaded in R6K-based suicide delivery vectors mobilizable by conjugation. Higher frequencies of insertions were obtained by using mini-Tn10 derivatives encoding kanamycin or gentamycin resistance. After applying this protocol, a multifunctional PPO-negative mutant was obtained. By using the antibiotic resistance cassette as a marker, flanking regions were cloned. Then the wild-type gene was amplified by PCR and was cloned and sequenced. This is the first report on cloning and sequencing of a gene encoding a prokaryotic enzyme with laccase activity. The deduced amino acid sequence shows the characteristic copper-binding sites of other blue copper proteins, including fungal laccases. In addition, it shows some extra copper-binding sites that might be related to its multipotent enzymatic capability.
 ...
PMID:Marinomonas mediterranea MMB-1 transposon mutagenesis: isolation of a multipotent polyphenol oxidase mutant. 1085 Sep 91

Sequencing of the genome of Ralstonia solanacearum revealed several genes that putatively code for polyphenol oxidases (PPOs). To study the actual expression of these genes, we looked for and detected all kinds of PPO activities, including laccase, cresolase, and catechol oxidase activities, in cellular extracts of this microorganism. The conditions for the PPO assays were optimized for the phenolic substrate, pH, and sodium dodecyl sulfate concentration used. It was demonstrated that three different PPOs are expressed. The genes coding for the enzymes were unambiguously correlated with the enzymatic activities detected by generation of null mutations in the genes by using insertional mutagenesis with a suicide plasmid and estimating the changes in the levels of enzymatic activities compared to the levels in the wild-type strain. The protein encoded by the RSp1530 locus is a multicopper protein with laccase activity. Two other genes, RSc0337 and RSc1501, code for nonblue copper proteins exhibiting homology to tyrosinases. The product of RSc0337 has strong tyrosine hydroxylase activity, and it has been shown that this enzyme is involved in melanin synthesis by R. solanacearum. The product of the RSc1501 gene is an enzyme that shows a clear preference for oxidation of o-diphenols. Preliminary characterization of the mutants obtained indicated that PPOs expressed by R. solanacearum may participate in resistance to phenolic compounds since the mutants exhibited higher sensitivity to L-tyrosine than the wild-type strain. These results suggest a possible role in the pathogenic process to avoid plant resistance mechanisms involving the participation of phenolic compounds.
 ...
PMID:Polyphenol oxidase activity expression in Ralstonia solanacearum. 1626 13