Location of three key enzymes of gluconeogenesis in baker's yeast

Abstract

The subcellular location of hexose diphosphatase, phosphoenolpyruvate carboxykinase and pyruvate carboxylase in baker's yeast (Saccharomyces cerevisiae) was investigated by density gradient centrifugation of spheroplast lysates obtained by osmotic shock treatment of spheroplasts and centrifugation for 10000 g x min. On the evidence obtained from zonal separations these three enzymes of gluconeogenesis are most probably located in the soluble cytosol.

Localization and kinetics of pyruvate-metabolizing enzymes in relation to aerobic alcoholic fermentation in Saccharomyces cerevisiae CBS 8066 and Candida utilis CBS 621

“…Subcelhilar fractiona~ion of S. cerevisiae showed that pyruvate carboxylase is a cytosolic enzyme in this organism, in confirmation with earlier studies [6,8]. However, in contrast to the report by Evans et al [9], also in C. utilis the enzyme was exclusively recovered in the soluble fraction (Table I).…”

“…However, the mitochondria were intact on the basis of various criteria and, furthermore, the enzyme was not detectable in the mitochondrial fraction. A cytosolic localization for pyruvate carboxylase in S. cerevisiae has also been reported by Haarasiha and Taskinen [6] and Lira et al [8]. Furthermore, no significant differences were found with respect to the kinetics of malate oxidation by isolated mitochondria.…”

“…on quantitative aspects of pyruvate metabolism. Of special interest was the localization of pyruvate carboxylase, in view of reported differences between S. cerevisiae and C. utilis [6][7][8][9]. Moreover, the regulation of f.he enzyme pyruvate decarboxylase by inorganic phosphate and other possible effectors was studied, since Boiteux and Hess [10] reported inhibition of this enzyme by phosphate.…”

A Biochemical Explanation for Lipid Accumulation in Candida 107 and Other Oleaginous Micro-organisms

“…For example, pyruvate carboxylase (enzyme 5 in scheme) might be in the cytoplasm as in baker's yeast (Haarasilta & Taskinen, 1977) though we have shown it in the mitochondrion which is its location in animal cells. There may be additional controls not examined in this work.…”

Fine control of the conversion of pyruvate (phosphoenolpyruvate) to oxaloacetate in various species

“…Such a linkage would be advantageous if the oxaloacetate formed is predominantly utilised for biosynthetic purposes rather than for an enhancement of cycle flux, and could therefore provide a mechanism whereby a balance can be achieved in the use of glucose (or lactate) carbon in the synthesis of lipids and of amino acids and pyrimidines (tig.2). In accord with this postulate current evidence suggests that in S. cerevisiae pyruvate carboxylase is localised in the cytosol [36] , rather than in the mitochondrion as is the case invertebrates and invertebrates [6,33,34] . E. coli PEP carboxylase fails to show the characteristic transient activation on exposure to long chain acylCoAs which has been taken to indicate a membrane association in the case of pyruvate carboxylase from a thermophilic Bacillus [28] .…”