Biosynthesis of 9-beta-D-arabinofuranosyladenine: hydrogen exchange at C-2' and oxygen exchange at C-3' of adenosine

Journal Article · Sat Apr 01 04:00:00 EST 1989 · Arch. Biochem. Biophys.; (United States)

DOI:https://doi.org/10.1016/0003-9861(89)90039-8· OSTI ID:6102174

Suhadolnik, R J; Pornbanlualap, S; Wu, J M; Baker, D C; Hebbler, A K

The data presented here describe new findings related to the bioconversion of adenosine to 9-beta-D-arabinofuranosyladenine (ara-A) by Streptomyces antibioticus by in vivo investigations and with a partially purified enzyme. First, in double label in vivo experiments with (2'-18O)- and (U-14C)adenosine, the 18O:14C ratio of the ara-A isolated does not change appreciably, indicating a stereospecific inversion of the C-2' hydroxyl of adenosine to ara-A with retention of the 18O at C-2'. In experiments with (3'-18O)- and (U-14C)-adenosine, (U-14C)ara-A was isolated; however, the 18O at C-3' is below detection. The adenosine isolated from the RNA from both double label experiments has essentially the same ratio of 18O:14C. Second, an enzyme has been isolated and partially purified from extracts of S. antibioticus that catalyzes the conversion of adenosine, but not AMP, ADP, ATP, inosine, guanosine, or D-ribose, to ara-A. In a single label enzyme-catalyzed experiment with (U-14C)adenosine, there was a 9.9% conversion to (U-14C)ara-A; with (2'-3H)-adenosine, there was a 8.9% release of the C-2' tritium from (2'-3H)adenosine which was recovered as 3H2O. Third, the release of 3H as 3H2O from (2'-3H)adenosine was confirmed by incubations of the enzyme with 3H2O and adenosine. Ninety percent of the tritium incorporated into the D-arabinose of the isolated ara-A was in C-2 and 8% was in C-3. The enzyme-catalyzed conversion of adenosine to ara-A occurs without added cofactors, displays saturation kinetics, a pH optimum of 6.8, a Km of 8 X 10(-4) M, and an inhibition by heavy metal cations. The enzyme also catalyzes the stereospecific inversion of the C-2' hydroxyl of the nucleoside antibiotic, tubercidin to form 7-beta-D-arabinofuranosyl-4-aminopyrrolo(2,3-d)pyrimidine. The nucleoside antibiotic, sangivamycin, in which the C-5 hydrogen is replaced with a carboxamide group, is not a substrate.

• Research Organization: Temple Univ. School of Medicine, Philadelphia, PA (USA)
• OSTI ID: 6102174
• Journal Information: Arch. Biochem. Biophys.; (United States), Journal Name: Arch. Biochem. Biophys.; (United States) Vol. 270:1; ISSN ABBIA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ADENINES
ADENOSINE
AMINES
ANTIMETABOLITES
AROMATICS
AZAARENES
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOSYNTHESIS
CARBON 14
CARBON 14 COMPOUNDS
CARBON ISOTOPES
CHROMATOGRAPHY
COUNTING TECHNIQUES
DOUBLE LABELLING
DRUGS
ELEMENTS
EVEN-EVEN NUCLEI
HETEROCYCLIC COMPOUNDS
HYDROGEN
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPE RATIO
ISOTOPES
LABELLED COMPOUNDS
LABELLING
LIGHT NUCLEI
METABOLISM
MICROORGANISMS
NONMETALS
NUCLEI
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PURINES
RADIOISOTOPES
RIBOSIDES
RNA
SCINTILLATION COUNTING
SEPARATION PROCESSES
STABLE ISOTOPES
STREPTOMYCES
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
WATER
YEARS LIVING RADIOISOTOPES