Two glucose-phosphorylating enzymes, a hexokinase phosphorylating both glucose and fructose, and a glucose-specific glucokinase were electrophoretically separated in the methylotrophic yeast Hansenula polymorpha. Hexokinase-negative, glucokinase-negative and double kinase-negative mutants were isolated in H. polymorpha by using mutagenesis, selection and genetic crosses. Regulation of synthesis of the sugar-repressed alcohol oxidase, catalase and maltase was studied in different hexose kinase mutants. In the wild type and in mutants possessing either hexokinase or glucokinase, glucose repressed the synthesis of maltase, alcohol oxidase and catalase. Glucose repression of alcohol oxidase and catalase was abolished in mutants lacking both glucose-phosphorylating enzymes (i.e. in double kinase-negative mutants). Thus, glucose repression in H. polymorpha cells requires a glucose-phosphorylating enzyme, either hexokinase or glucokinase. The presence of fructose-phosphorylating hexokinase in the cell was specifically needed for fructose repression of alcohol oxidase, catalase and maltase. Hence, glucose or fructose has to be phosphorylated in order to cause repression of the synthesis of these enzymes in H. polymorpha suggesting that sugar repression in this yeast therefore relies on the catalytic activity of hexose kinases.

• MeSH
• biologické modely MeSH
• deoxyglukosa farmakologie   MeSH
• fosforylace MeSH
• fruktosa metabolismus   MeSH
• geny hub MeSH
• glukokinasa genetika   metabolismus   MeSH
• glukosa metabolismus   farmakologie   MeSH
• hexokinasa genetika   metabolismus   MeSH
• hybridizace genetická MeSH
• kinetika MeSH
• mutace * MeSH
• Pichia účinky léků   enzymologie   genetika   růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• deoxyglukosa MeSH
• fruktosa MeSH
• glukokinasa MeSH
• glukosa MeSH
• hexokinasa MeSH

Regulation of the synthesis of maltase and methanol-oxidizing enzymes by the carbon source has been analyzed in the methylotrophic yeast Hansenula polymorpha. Maltase was shown to be responsible for the growth of H. polymorpha not only on maltose, but also on sucrose. The affinity of maltase towards maltase substrates decreased in the order: 4-nitrophenyl glucoside (PNPG) < sucrose < maltose. Mutants with glucose repression-insensitive synthesis of alcohol oxidase and maltase were obtained from H. polymorpha by mutagenesis and subsequent selection on methanol medium in the presence of 2-deoxy-D-glucose. One of the isolated mutants, L63, was studied in more detail. Mutant L63 was recessive and monogenic and it was not deficient in hexokinase. Its analysis revealed that H. polymorpha most probably has a repressor protein that in the presence of glucose can down-regulate expression of both maltase and enzymes of methanol oxidation.

• MeSH
• alfa-glukosidasy biosyntéza   genetika   metabolismus   MeSH
• alkoholoxidoreduktasy biosyntéza   genetika   metabolismus   MeSH
• bakteriální proteiny metabolismus   MeSH
• enzymová represe MeSH
• glukosa metabolismus   farmakologie   MeSH
• kultivační média MeSH
• methanol metabolismus   MeSH
• oxidace-redukce MeSH
• Pichia enzymologie   genetika   růst a vývoj   MeSH
• regulace genové exprese u hub * MeSH
• represorové proteiny metabolismus   MeSH
• substrátová specifita MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• alcohol oxidase MeSH Prohlížeč
• alfa-glukosidasy MeSH
• alkoholoxidoreduktasy MeSH
• bakteriální proteiny MeSH
• glukosa MeSH
• kultivační média MeSH
• methanol MeSH
• represorové proteiny MeSH