title: Poly(A) polymerase from Vigna unguiculata seedlings. A bifunctional enzyme responsible for both poly(A)-polymerizing and poly(A)-hydrolyzing activities.
abstract: Poly(A)-specific ribonuclease was co-purified with poly(A) polymerase from Vigna unguiculata seedlings. Both activities were separated into two forms (enzymes I and II) by a final hydrophobic column chromatography. The enzyme I preparation, which was homogeneous as examined by SDS/PAGE, had both poly(A) polymerase and poly(A)-specific ribonuclease activities. The antibody raised to the enzyme I preparation precipitated both enzyme activities. These indicate that a single polypeptide (Mr 63,000) is responsible for both poly(A)-polymerizing and poly(A)-hydrolyzing activities. The poly(A)-specific ribonuclease was a 3'-exonuclease specific to single-stranded poly(A), forming 5'AMP as the sole reaction product. The hydrolytic activity required either Mn2+ or Mg2+ with different optimum concentrations, whereas the polymerizing activity required Mn2+ but not Mg2+. ATP and PPi had little or no effect on the poly(A)-specific ribonuclease activity.
authors.affiliation: Department of Biology, Tokyo Metropolitan University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tarui
authors.forename: T
authors.initials: T
authors.lastname: Minamikawa
mesh_terms: D002413:Cations, Divalent; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D005095:Exoribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D009713:Nucleotidyltransferases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D011061:Poly A / Q000096:biosynthesis / Q000378:metabolism*; D011062:Polynucleotide Adenylyltransferase / Q000302:isolation & purification / Q000378:metabolism*; D012265:Ribonucleotides / Q000494:pharmacology; D013379:Substrate Specificity
chemical_list: D002413:Cations, Divalent; D005095:Exoribonucleases; D009713:Nucleotidyltransferases; D011061:Poly A; D011062:Polynucleotide Adenylyltransferase; D012265:Ribonucleotides