Malate transport in Schizosaccharomyces pombe.
The transport of malate was studied in a Schizosaccharomyces pombe wild-type strain and in mutant strains unable to utilize malic acid. Two groups of such mutants, i.e., malic enzyme-deficient and malate transport-defective mutants, were differentiated by a 14C-labeled L-malate transport assay and by starch gel electrophoresis followed by activity staining for malic enzyme (malate dehydrogenase [oxaloacetate decarboxylating] [NAD+]; 1.1.1.38) and malate dehydrogenase (1.1.1.37). Transport of malate in S. pombe was constitutive and strongly inhibited by inhibitors of oxidative phosphorylation and of the formulation of proton gradients. Transport was a saturable function of the malate concentration. The apparent Km and Vmax values for transport by the parent were 3.7 mM and 40 nmol/min per mg of protein, respectively, while those of the malic enzyme-deficient mutant were 5.7 mM and 33 nmol/min per mg of protein, respectively. Malate transport was pH and temperature dependent. The specificity of transport was studied with various substrates, including mono- and dicarboxylic acids, and the possibility of a common transport system for dicarboxylic acids is discussed.
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008293:Malates / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D004718:Saccharomycetales / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D013696:Temperature
D001426:Bacterial Proteins; D002352:Carrier Proteins; D008293:Malates; C030298:malic acid