title: A second form of adenine phosphoribosyltransferase in Arabidopsis thaliana with relative specificity towards cytokinins.
abstract: Adenine phosphoribosyltransferase (APRTase) is an important enzyme for its ability to convert adenine, a byproduct of many biochemical reactions, into AMP. By functional complementation of an Escherichia coli mutant, cDNAs encoding two APRTases have been cloned from Arabidopsis thaliana. One of the cDNAs (ATapt1) has been previously identified while the second (ATapt2) is of a previously unknown type. Kinetic analysis of the two enzymes purified from E. coli expressing the two cDNAs indicates that ATapt2 has a higher affinity for cytokinin than the ATapt1. RNase protection studies indicate that the ATapt2, is not expressed in leaves. Analysis of the gene structure indicates that ATapt2 has identical intron positions to ATapt1, but neither the intron sequence nor intron size are conserved between the two genes. The implications of a second, differentially expressed APRTase with affinity for both adenine and cytokinin are discussed.
authors.affiliation: Laboratoire de Biologie Cellulaire, INRA Institut National de Recherche Agronomique, Versailles, France.
authors.forename: K M
authors.initials: KM
authors.lastname: Schnorr
authors.forename: C
authors.initials: C
authors.lastname: Gaillard
authors.forename: E
authors.initials: E
authors.lastname: Biget
authors.forename: P
authors.initials: P
authors.lastname: Nygaard
authors.forename: M
authors.initials: M
authors.lastname: Laloue
mesh_terms: D000228:Adenine Phosphoribosyltransferase / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology*; D001483:Base Sequence; D003001:Cloning, Molecular; D003583:Cytokinins / Q000378:metabolism*; D018076:DNA, Complementary; D018744:DNA, Plant / Q000737:chemistry; D004926:Escherichia coli; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D003583:Cytokinins; D018076:DNA, Complementary; D018744:DNA, Plant; D007527:Isoenzymes; D011994:Recombinant Proteins; D000228:Adenine Phosphoribosyltransferase