Isolation and properties of genetically defined strains of the methylotrophic yeast Hansenula polymorpha CBS4732

Genetically defined strains of the yeast Hansenula polymorpha were constructed froth a clone of H. polymorpha CBS4732 with very low mating and sporulation abilities. Mating, spore viability, and the percentage of four-spore-containing asci were increased to a level at which tetrad analysis was possible. Auxotrophic mutations in 30 genes were isolated and used to construct strains with multiple markers for mapping studies, transformation with plasmid DNA, and mutant screening. Various other types of mutants were isolated and characterized, among them mutants that displayed an altered morphology, methanol-utilization deficient mutants and strains impaired in the biosynthesis of alcohol oxidase and catalase. Also, the mutability of H. polymorpha CBS4732 vs H. polymorpha NCYC495 was compared. The data revealed clear differences in frequencies of appearance and mutational spectra of some mutants isolated. Many of the mutants isolated had good mating abilities, and diploids resulting from their crossing displayed high sporulation frequencies and high spore viability. Most of the markers used revealed normal Mendelian segregation during meiosis. The frequency of tetratype spore formation was lower than in Saccharomyces cerevisiae suggesting a lower frequency of recombination during the second meiotic division. The properties of genetically defined strains of H. polymorpha CBS4732 as well as their advantages for genetics and molecular studies are discussed

Construction of uricase-overproducing strains of Hansenula polymorpha and its application as biological recognition element in microbial urate biosensor

<p>Abstract</p> <p>Background</p> <p>The detection and quantification of uric acid in human physiological fluids is of great importance in the diagnosis and therapy of patients suffering from a range of disorders associated with altered purine metabolism, most notably gout and hyperuricaemia. The fabrication of cheap and reliable urate-selective amperometric biosensors is a challenging task.</p> <p>Results</p> <p>A urate-selective microbial biosensor was developed using cells of the recombinant thermotolerant methylotrophic yeast <it>Hansenula polymorpha </it>as biorecognition element. The construction of uricase (UOX) producing yeast by over-expression of the uricase gene of <it>H. polymorpha </it>is described. Following a preliminary screening of the transformants with increased UOX activity in permeabilized yeast cells the optimal cultivation conditions for maximal UOX yield namely a 40-fold increase in UOX activity were determined.</p> <p>The UOX producing cells were coupled to horseradish peroxidase and immobilized on graphite electrodes by physical entrapment behind a dialysis membrane. A high urate selectivity with a detection limit of about 8 μM was found.</p> <p>Conclusion</p> <p>A strain of <it>H. polymorpha </it>overproducing UOX was constructed. A cheap urate selective microbial biosensor was developed.</p

In vitro inhibition effect of some chalcones on erythrocyte carbonic anhydrase I and II

Gencer, Nahit/0000-0001-7092-8857WOS: 000329843900005PubMed: 23330659In this study, 4'-(phenylurenyl/thiourenyl) chalcones (14-25) were prepared from 4'-(phenylurenyl/thiourenyl)acetophenones and benzaldehyde derivatives by Claisen-Schmidt condensation. In vitro inhibition effects of chalcone derivatives on purified carbonic anhydrase I and carbonic anhydrase II were investigated by using the CO2 hydration method of Maren. The result showed that all the synthesized compounds inhibited the CA isoenzymes activity. 18 and 19 were found to be most active (IC50 = 25.41 m M and 23.06 mu M) for hCA I, respectively. For hCA II, 24 is the most active compound (IC50 = 14.40 mu M)