Presence of the molybdenum-cofactor in nitrate reductase-deficient mutant cell lines of Nicotiana tabacum

摘要: Nicotiana tabacum mutant cell cultures lacking nitrate reductase activity were assayed for the presence of molybdenum-cofactor using its ability to restore NADPH-nitrate in extracts Neurospora crassa nit-1 mycelia. The tobacco wild-type line was shown complement efficiently N. vitro. seems exist a bound form, as acid-treatment required release cofactor activity. Molybdate (5–10 mM), ascorbic acid, and anaerobic conditions greatly increased cofactor, demonstrating high lability sensitivity oxygen. Similar results obtained with two nia mutants, which are defective apoprotein reductase. four cnx mutants studied contain exclusively an inactive form molybdenum-cofactor. This could be reactivated vitro vivo by unphysiologically concentrations molybdate (1–10 thereby converting cells into highly active sources vitro, restoring xanthine dehydrogenase partial acitivity. Thus defect resides lack molybdenum catalytically ligand metal while structural moiety not impaired mutation. subunit assembly found independent content cofactor.