Transport of L-glutamic acid in the fission yeast Schizosaccharomyces pombe.
Transport of L-glutamic acid into the fission yeast Schizosaccharomyces pombe grown to the early stationary phase and preincubated for 60 min with 1% D-glucose is practically unidirectional and is mediated by a single uphill transport system with a KT of 170 microM and Jmax of 4.8 nmol min-1 (mg dry wt.)-1. The system proved to be rather non-specific since all the amino acids transported into the cells acted as potent competitive inhibitors. It has a pH optimum at 3.0-4.0, the accumulation ratio of L-glutamic acid is highest at a suspension density of 0.6-1.0 mg dry wt. per ml and decreases with increasing L-glutamic acid concentrations in the external medium. The system present in the cells after preincubation with D-glucose is unstable and its activity decays after washing the cells with water or after stopping the cytosolic proteinsynthesis with cycloheximide, with a half-time of 24 min in a reaction significantly retarded by phenylmethylsulfonyl fluoride, a serine proteinase inhibitor. The synthesis of the transport protein appears to be repressible by ammonium ions.
Department of Membrane Transport, Czechoslovak Academy of Sciences, Prague.
K
K
Rezková
J
J
Horák
H
H
Sychrová
A
A
Kotyk
D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D005971:Glutamates / Q000737:chemistry / Q000378:metabolism*; D018698:Glutamic Acid; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012568:Schizosaccharomyces / Q000187:drug effects / Q000378:metabolism*; D013379:Substrate Specificity
D002352:Carrier Proteins; D005656:Fungal Proteins; D005971:Glutamates; D018698:Glutamic Acid; D003513:Cycloheximide