Dihydroxyacetone kinase of methanol-assimilating yeasts. I. Regulation of dihydroxyacetone kinase from Candida methylica in situ

✍ Scribed by K. H. Hofmann; Dr. W. Babel

• Book ID: 102909368
• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 696 KB
• Volume: 20
• Category: Article
• ISSN: 0233-111X
• DOI: 10.1002/jobm.19800200605

✦ Synopsis

Abstract

In order to investigate the control behaviour of dihydroxyacetone kinase of methanol‐grown Candida methylica under nearly physiological conditions kinetic and regulatory studies were carried out in situ. Yeast cells were made permeable to substrate and reaction products by treatment with Triton X‐100. Normal Michaelis‐Menten kinetics resulted in dependence upon the dihydroxyacetone concentration, both at the pH optimum of 7.6 and near the physiological pH‐value of 6.5. The K~m~ obtained for dihydroxyacetone was 0.02 mm, independent of the pH‐value. The plots of dihydroxyacetone kinase activity as a function of the ATP concentration revealed complex kinetic characteristics with plateau regions. The maximum reaction rate was reached only after a lag time both at pH 7.6 and concentrations of ATP higher than 5 mm and at pH 6.5 and concentrations of ATP higher than 1.25 mm. Among a great number of tested metabolites no inhibitors of dihydroxyacetone kinase were found. Dihydroxyacetone kinase activity depending upon energy charge according to Atkinson exhibited curves of the U‐type. These results and further data concerning the regulation of other enzymes obtained with C. methylica and other yeasts were the basis to propose a preliminary overall model of fine control of the carbon and energy metabolism of methanol‐utilizing yeasts.