Photochemical studies and ultraviolet sensitization of Escherichia coli Thymidylate kinase by various halogenated substrate analogs

Journal Article · Thu Jan 01 04:00:00 UTC 1976 · J. Biol. Chem.; (United States)

OSTI ID:6452966

Chen, M S; Chang, P K; Prusoff, W H

The effect of 5-iodo-2'-deoxyuridine monophosphate (IdUMP), various 5-halogenated-5'-azido-2',5'-dideoxyuridine derivatives, 2'-deoxy-6-azauridine (AzdUrd), and its halogenated analogs on the ultraviolet sensitization of Escherichia coli thymidylate kinase has been investigated. Only those compounds iodinated in position 5 enhance the rate of ultraviolet inactivation of this enzyme. However, 5'-azido nucleosides with iodo, bromo, chloro, or fluoro substituents in position 5 neither protect nor sensitize thymidylate kinase to ultraviolet inactivation. Thymidine 5'-monophosphate partially protects the enzyme against ultraviolet inactivation either in the presence or absence of ultraviolet-sensitizing iodinated analogs. Magnesium ion does not enhance the ultraviolet inactivation of thymidylate kinase by 5-iodinated nucleoside analogs. The kinetic data support an active site-directed enhancement of the enzyme to ultraviolet inactivation by 5-iodo-2'-deoxyuridine monophosphate, since the concentration of IdUMP required to attain 50% maximal enhancement is 0.24 mM which is in good agreement with its K/sub i/ of 0.18 mM. When either (/sup 125/I)IdUMP or (2-/sup 14/C)IdUMP was irradiated with the enzyme, both radioactivities were associated with the enzyme, however only with the /sup 14/C analog was the amount bound at half-saturation essentially equal to the amount required to inactivate the enzyme by 50%. These data support the hypothesis that the active entity in the enhancement by IdUMP of thymidylate kinase inactivation during ultraviolet irradiation is the uridylate free radical which is formed photochemically from IdUMP.

• Research Organization: Yale Univ. School of Medicine, New Haven, CT
• OSTI ID: 6452966
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 251:21; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
560111* -- Radiation Effects on Biochemicals-- In Vitro-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANTIMETABOLITES
ANTIMITOTIC DRUGS
ATOMIC IONS
AZINES
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
CARBON 14
CARBON ISOTOPES
CHARGED PARTICLES
CHEMISTRY
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTROMAGNETIC RADIATION
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
ESCHERICHIA COLI
EVEN-EVEN NUCLEI
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INACTIVATION
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
IODODEOXYURIDINE
IODOURACILS
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MAGNESIUM IONS
MICROORGANISMS
NUCLEI
NUCLEOSIDES
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHOTRANSFERASES
PHOTOCHEMISTRY
PYRIMIDINES
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
RADIOSENSITIVITY EFFECTS
REACTION KINETICS
RIBOSIDES
TRACER TECHNIQUES
TRANSFERASES
ULTRAVIOLET RADIATION
URACILS
YEARS LIVING RADIOISOTOPES