Pyruvate dehydrogenase kinase

About: Pyruvate dehydrogenase kinase is a research topic. Over the lifetime, 4224 publications have been published within this topic receiving 161052 citations. The topic is also known as: [pyruvate dehydrogenase (lipoamide)] kinase & pyruvate dehydrogenase (lipoamide) kinase.

Participation of acetaldehyde dehydrogenases in ethanol and pyruvate metabolism of the yeast Saccharomyces cerevisiae.

Abstract: This work was undertaken to clarify the role of acetaldehydedehydrogenases in Saccharomyces cerevisiae metabolismduring growth on respiratory substrates. Until now, there hasbeen little agreement concerning the ability of mutantsdeleted in gene ALD4, encoding mitochondrial acetaldehydedehydrogenase, to grow on ethanol. Therefore we con-structed mutants in two parental strains (YPH499 andW303-1a). Some differences appeared in the growthcharacteristics of mutants obtained from these two parentalstrains. For these experiments we used ethanol, pyruvate orlactate as substrates. Mitochondria can oxidize lactate intopyruvate using an ATP synthesis-coupled pathway. Theald4Dmutant derived from the YPH499 strain failed togrow on ethanol, but growth was possible for the ald4Dmutant derived from the W303-1a strain. The co-disruptionof ALD4 and PDA1 (encoding subunit E1a of pyruvatedehydrogenase) prevented the growth on pyruvate for bothstrains but prevented growth on lactate only in the doublemutant derived from the YPH499 strain, indicating that themutation effects are strain-dependent. To understand thesedifferences, we measured the enzyme content of thesedifferent strains. We found the following: (a) the activity ofcytosolic acetaldehyde dehydrogenase in YPH499 wasrelatively low compared to the W303-1a strain; (b) it waspossible to restore the growth of the mutant derived fromYPH499 either by addition of acetate in the media or byintroduction into this mutant of a multicopy plasmidcarrying the ALD6 gene encoding cytosolic acetaldehydedehydrogenase. Therefore, the lack of growth of the mutantderived from the YPH499 strain seemed to be related to thelow activity of acetaldehyde oxidation. Therefore, whencultured on ethanol, the cytosolic acetaldehyde dehydro-genase can partially compensate for the lack of mitochon-drial acetaldehyde dehydrogenase only when the activity ofthe cytosolic enzyme is sufficient. However, when culturedon pyruvate and in the absence of pyruvate dehydrogenase,the cytosolic acetaldehyde dehydrogenase cannot compen-sate for the lack of the mitochondrial enzyme because themitochondrial form produces intramitochondrial NADH andconsequently ATP through oxidative phosphorylation.Keywords: Saccharomycescerevisiae; acetaldehydedehydro-genase; pyruvate dehydrogenase.This work was undertaken to clarify the role of acetaldehydedehydrogenases in Saccharomyces cerevisiae metabolismduring growth on respiratory substrates. Three conversionpathways of pyruvate into acetyl-CoA have been describedin yeast (Fig. 1). The pyruvate dehydrogenase complexlocated inside the mitochondrial matrix converts pyruvateinto acetyl-CoA with the production of NADH. This com-plex has been purified from S. cerevisiae [1,2] and its expres-sion is independent of the carbon source used for growth [3].Another metabolic pathway occurs via the cytosolic pyru-vate dehydrogenase bypass [4] and requires the followingenzymes: pyruvate decarboxylase, cytosolic acetaldehydedehydrogenase and acetyl-CoA synthase. All these enzymesare located in the cytosol. This appears to be an alternativepathway for the production of cytoplasmic acetyl-CoA forbiosynthesis. Recently, a mitochondrial pyruvate dehydro-genase bypass was described, showing that pyruvate can beoxidized inside mitochondria by a pathway involving mito-chondrial acetaldehyde dehydrogenase [5]. Pyruvate is firstdecarboxylated to acetaldehyde in the cytosol by pyruvatedecarboxylase and is then oxidized by mitochondrial acet-aldehyde dehydrogenase, leading to the reduction of NAD

Enzyme activities of human erythrocyte ghosts: effects of various treatments.

Abstract: Ghosts of human erythrocytes prepared by hypotonic hemolysis were assayed for aldolase, triosephosphate isomerase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, pyruvate kinase, lactate dehydrogenase, and glutathione peroxidase and reductase. Cryptic activity of the enzymes was demonstrated by an increase in activity on dilution with water, which caused fragmentation of the ghosts. Aldolase and glyceraldehyde phosphate dehydrogenase were classed as firmly bound; phosphoglycerate kinase was intermediate; the others were loosely bound. Triton X-100 increased the activities of aldolase, glyceraldehyde phosphate dehydrogenase, and phosphoglycerate kinase. The pH of the medium had little effect upon the firmly bound enzymes but it markedly affected the retention of hemoglobin and the activities of the loosely bound enzymes. The presence of Mg or Ca ions enhanced the retention of hemoglobin and the activity of lactate dehydrogenase and pyruvate kinase, with little effect on aldolase and glyceraldehyde phosphate dehydrogenase. Ghosts diluted in water disintegrated into fragments and tubules or vesicles; Mg or Ca at 1mm afforded protection against this. When ghosts were treated with Triton X-100 and adenosine triphosphate, they contracted to about one-seventh of their volume. The shrunken ghosts had lost a considerable proportion of their cholesterol and protein to the medium.