PvdP is a tyrosinase that drives maturation of the pyoverdine chromophore in Pseudomonas aeruginosa.

The iron binding siderophore pyoverdine constitutes a major adaptive factor contributing to both virulence and survival in fluorescent pseudomonads. For decades, pyoverdine production has allowed the identification and classification of fluorescent and nonfluorescent pseudomonads. Here, we demonstrate that PvdP, a periplasmic enzyme of previously unknown function, is a tyrosinase required for the maturation of the pyoverdine chromophore in Pseudomonas aeruginosa.

Therapeutic resistance to angiotensin converting enzyme (ACE) inhibition is related to pharmacodynamic and -kinetic factors in 5/6 nephrectomized rats.

Proteinuria plays a pathogenic role in the development of end stage renal disease. Angiotensin converting enzyme (ACE) inhibitors lower proteinuria and are renoprotective. However, large inter-individual variation in antiproteinuric response to ACE inhibitors exists.

Development of a multiplex non-radioactive receptor assay: the benzodiazepine receptor, the serotonin transporter and the beta-adrenergic receptor.

Binding assays still form a fundamental part of modern drug development. Receptor binding assays are mostly based on radioactivity because of their speed, ease of use and reproducibility. Disadvantages, such as health hazards and production of radioactive waste, have prompted the development of non-radioactive receptor binding assays.

Identification of the catalytic residues of alpha-amino acid ester hydrolase from Acetobacter turbidans by labeling and site-directed mutagenesis.

The alpha-amino acid ester hydrolase from Acetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing the side chain peptide bond in beta-lactam antibiotics. Data base searches revealed that the enzyme contains an active site serine consensus sequence Gly-X-Ser-Tyr-X-Gly that is also found in X-prolyl dipeptidyl aminopeptidase. The serine hydrolase inhibitor p-nitrophenyl-p'-guanidino-benzoate appeared to be an active site titrant and was used to label the alpha-amino acid ester hydrolase.

On-line coupling of solid-phase extraction with mass spectrometry for the analysis of biological samples. I. Determination of clenbuterol in urine.

The potential of the direct coupling of solid-phase extraction (SPE) with mass spectrometry (MS) for the analysis of biological samples is demonstrated. For SPE a cartridge exchanger is used and the eluate is directly introduced into the mass spectrometer. This system has been investigated for the determination of clenbuterol in urine.

Reconstruction of the proteolytic pathway for use of beta-casein by Lactococcus lactis.

Amino acid auxotrophous bacteria such as Lactococcus lactis use proteins as a source of amino acids. For this process, they possess a complex proteolytic system to degrade the protein(s) and to transport the degradation products into the cell. We have been able to dissect the various steps of the pathway by deleting one or more genes encoding key enzymes/components of the system and using mass spectrometry to analyse the complex peptide mixtures.

The extracellular PI-type proteinase of Lactococcus lactis hydrolyzes beta-casein into more than one hundred different oligopeptides.

The peptides released from beta-casein by the action of PI-type proteinase (PrtP) from Lactococcus lactis subsp. cremoris Wg2 have been identified by on-line coupling of liquid chromatography to mass spectrometry. After 24 h of incubation of beta-casein with purified PrtP, a stable mixture of peptides was obtained.

Histidine 289 is essential for hydrolysis of the alkyl-enzyme intermediate of haloalkane dehalogenase.

Haloalkane dehalogenase (DhlA) from Xanthobacter autotrophicus GJ10 catalyzes the hydrolytic cleavage of carbon-halogen bonds in a broad range of halogenated aliphatic compounds. Previous work has shown that Asp124, which is located close to the internal substrate-binding cavity, carries out a nucleophilic attack on the C-alpha of the alkylhalide, displacing the halogen. The resulting alkyl-enzyme intermediate is subsequently hydrolyzed.

Demonstration by mass spectrometry that pseudo-hevein and hevein have ragged C-terminal sequences.

The primary structure of pseudo-hevein, a minor hevein component from the latex of the rubber tree, Hevea brasiliensis, was determined. Six differences with the sequence of the major hevein component were found, one of which is a replacement of tryptophan by tyrosine in the carbohydrate binding region of the molecule. Analysis by ion-spray mass spectrometry showed that pseudo-hevein has a heterogeneous C-terminal extension of several glycine residues and that hevein itself also contains minor components with additional C-terminal amino-acid residues.

Site-directed mutagenesis and oxygen isotope incorporation studies of the nucleophilic aspartate of haloalkane dehalogenase.

Haloalkane dehalogenase catalyzes the hydrolytic cleavage of carbon-halogen bonds in a broad range of halogenated aliphatic compounds. The X-ray structure suggests that Asp124, which is located close to an internal cavity, carries out a nucleophilic attack on the C alpha of the substrate, releasing the halogen. To study the mechanism of hydrolysis, this aspartate residue was mutated to alanine, glycine, or glutamate.