Publications

• A mechanized urease activity assay.

  Bzura J., Koncki R.

  Two fully mechanized flow analysis systems for urease activity assays have been developed, characterized and compared. Both of them are based on almost the same compact system of solenoid micropumps and microvalves controlled and actuated by highly effective, low-power and economic Arduino microco ... >> More

  Two fully mechanized flow analysis systems for urease activity assays have been developed, characterized and compared. Both of them are based on almost the same compact system of solenoid micropumps and microvalves controlled and actuated by highly effective, low-power and economic Arduino microcontroller. For photometric detection of ammonia formed in the course of enzymatic hydrolysis of urea, the Berthelot method and the Nessler reaction have been examined. For both these detection schemes very simple dedicated optoelectronic flow-through detectors made of paired light emitting diodes have been developed. In both systems single enzyme assay lasting a few minutes allows determination of urease in activity range 0.02-5.3 U mL^-1 with detection limit 0.02 U mL^-1 and in 1.3-5.3 U mL^-1 range with 0.75 U mL^-1 detection limit for Nessler reaction and Berthelot method based systems, respectively. When compared with mechanized Berthelot method, the bioanalytical system based on Nessler reaction offers higher sensitivity, lower detection/determination limits, better selectivity and lower cost of the assay. It has been demonstrated that the developed bioanalytical flow systems could be useful for urease determination in complex biological matrix like plant extracts and media for microbial cultures as well as for inhibitive determination of heavy metals at sub-ppm levels. << Less

  Enzyme Microb Technol 123:1-7(2019) [PubMed] [EuropePMC]

• Metal ions in enzymes using ammonia or amides.

  Dixon N.E., Gazzola C., Blakeley R.L., Zerner B.

  In an attempt to understand the role of nickel in jack bean urease (1), we turned to a variety of other enzymes important in the utilization, production, or transfer of ammonia. We found several, including the L-histidine and L-phenylalanine ammonialyases and some enzymes that utilize glutamine or ... >> More

  In an attempt to understand the role of nickel in jack bean urease (1), we turned to a variety of other enzymes important in the utilization, production, or transfer of ammonia. We found several, including the L-histidine and L-phenylalanine ammonialyases and some enzymes that utilize glutamine or ammonia in amidotransferase reactions, all of which show evidence for the involvement of as yet unreported transition metal ions in their mechanism of action. We support the view that catalysis by metalloenzymes may be a reflection of the chemistry of the metal ion itself as a Lewis acid, and that perhaps too much emphasis has been placed on supposed special characteristics (such as strains, "entasis") of the enzyme-metal ion association. In this context, we have discussed the mechanism of catalysis of hydrolysis of specific substrates by carboxypeptidase A, and have returned to urease to examine the role of nickel in its mechanism of action. << Less

  Science 191:1144-1150(1976) [PubMed] [EuropePMC]

• Ureases: Historical aspects, catalytic, and non-catalytic properties - A review.

  Kappaun K., Piovesan A.R., Carlini C.R., Ligabue-Braun R.

  Urease (urea amidohydrolase, EC 3.5.1.5) is a nickel-containing enzyme produced by plants, fungi, and bacteria that catalyzes the hydrolysis of urea into ammonia and carbamate. Urease is of historical importance in Biochemistry as it was the first enzyme ever to be crystallized (1926). Finding nic ... >> More

  Urease (urea amidohydrolase, EC 3.5.1.5) is a nickel-containing enzyme produced by plants, fungi, and bacteria that catalyzes the hydrolysis of urea into ammonia and carbamate. Urease is of historical importance in Biochemistry as it was the first enzyme ever to be crystallized (1926). Finding nickel in urease's active site (1975) was the first indication of a biological role for this metal. In this review, historical and structural features, kinetics aspects, activation of the metallocenter and inhibitors of the urea hydrolyzing activity of ureases are discussed. The review also deals with the non-enzymatic biological properties, whose discovery 40 years ago started a new chapter in the study of ureases. Well recognized as virulence factors due to the production of ammonia and alkalinization in diseases by urease-positive microorganisms, ureases have pro-inflammatory, endocytosis-inducing and neurotoxic activities that do not require ureolysis. Particularly relevant in plants, ureases exert insecticidal and fungitoxic effects. Data on the jack bean urease and on jaburetox, a recombinant urease-derived peptide, have indicated that interactions with cell membrane lipids may be the basis of the non-enzymatic biological properties of ureases. Altogether, with this review we wanted to invite the readers to take a second look at ureases, very versatile proteins that happen also to catalyze the breakdown of urea into ammonia and carbamate. << Less

  J Adv Res 13:3-17(2018) [PubMed] [EuropePMC]

• Urease from Staphylococcus saprophyticus: purification, characterization and comparison to Staphylococcus xylosus urease.

  Schaefer U.K., Kaltwasser H.

  Urease from Staphylococcus saprophyticus was purified more than 800-fold by liquid chromatography reaching homogeneity, as shown by isoelectric focussing, at a maximum specific activity of 1979 U/mg. The molecular weight of the native enzyme was 420,000; it consisted of subunits with molecular wei ... >> More

  Urease from Staphylococcus saprophyticus was purified more than 800-fold by liquid chromatography reaching homogeneity, as shown by isoelectric focussing, at a maximum specific activity of 1979 U/mg. The molecular weight of the native enzyme was 420,000; it consisted of subunits with molecular weights of 72,400 (alpha), 20,400 (beta), 13,900 (gamma) in an estimated (alpha beta gamma)4 stoichiometry. In native gradient polyacrylamide gel electrophoresis urease exhibited a multiple activity band pattern with molecular weights ranging from 420,000 to 100,000. In the native enzyme, 4.09 (+/-0.25) atoms of nickel per molecule were detected. The N-terminal amino acids of the urease subunits were identical to those from Staphylococcus xylosus, and amino acid analysis revealed high similarities in both enzymes; no cysteine was detected after acid hydrolysis of vinylpyridinylated urease. Electron micrographs of negatively stained urease specimens from both staphylococci showed identical size and structure. << Less

  Arch. Microbiol. 161:393-399(1994) [PubMed] [EuropePMC]