title: Evidence for messenger ribonucleic acid of an ammonium-inducible glutamate dehydrogenase and synthesis, covalent modification, and degradation of enzyme subunits in uninduced Chlorella sorokiniana cells.
abstract: The cells of Chlorella sorokiniana cultured in nitrate medium contain no detectable catalytic activity of an ammonium-inducible nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (NADP-GDH). However, several lines of experimental evidence indicated that the NADP-GDH messenger ribonucleic acid was present at high levels and was being translated in uninduced cells. First, binding studies with 125I-labeled anti-NADP-GDH immunoglobulin G and total polysomes isolated from uninduced and induced cells showed that NADP-GDH subunits were being synthesized on polysomes from both types of cells. Second, when polyadenylic acid-containing ribonucleic acid was extracted from polysomes from uninduced and induced cells and placed into a messenger ribonucleic acid-dependent in vitro translation system, NADP-GDH subunits were synthesized from the ribonucleic acid from both sources. Third, when ammonia was added to uninduced cells, NADP-GDH antigen accumulated without an apparent induction lag. Fourth, by use of a specific immunoprecipitation procedure coupled to pulse-chase studies with [35S]sulfate, it was shown that the NADP-GDH subunits are rapidly synthesized, covalently modified, and then degraded in uninduced cells.
mesh_terms: D000645:Ammonium Sulfate; D002708:Chlorella / Q000201:enzymology*; D003470:Culture Media; D004790:Enzyme Induction; D005969:Glutamate Dehydrogenase / Q000378:metabolism*; D009249:NADP / Q000494:pharmacology; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: D003470:Culture Media; D012333:RNA, Messenger; D009249:NADP; D005969:Glutamate Dehydrogenase; D000645:Ammonium Sulfate